I've been through this as the parent of a son who played four years of baseball in the ACC while majoring in Mechanical Engineering, and a daughter who rowed for 2.5 years and is starting Med School in a couple of weeks.
To address your questions:
1. Did son/daughter shy away from difficult majors? No. Frankly, I suggested my son consider math or physics instead of engineering. But, he was convinced he could do it and play baseball. He was right.
2. Did anyone push them away from a difficult major? Other than me, no. The coaches were fine with him majoring in engineering. I think they realize that a lot of kids will change majors after the first year anyway, so why not let them try it and find out for themselves. However, I have a friend whose son was recruited at Duke and the coaching staff at that time flat out told him he could not major in engineering and play baseball. But, the regime has changed, so that may no longer be the case.
3. How did he handle it? Lots of late nights studying. But, more on that below.
Random thoughts:
From what I have seen, there are 3 factors that may determine whether your son or daughter can handle engineering or pre-med while playing a sport: (1) How good a student he/she is. Some kids are very bright, but never learn how to study in HS. This will have to change quickly. (2) Determination/Commitment. A determined kid can overcome all sorts of obstacles. (3) Raw intelligence. IQ points make everything easier.
My son is very bright, but only a fair student. He never really cared about grades. They just came easily in HS. This will not happen with an engineering major, no matter how smart you are. He received a good bit of academic money to attend college. This required that he maintain a 3.0. He did that into his senior year, then he got a little senioritis and dipped below 3.0. (More on that later). He spent a lot of late nights studying, but he didn't miss any football games or many parties. Although there was one night that he threw a bat through a wall because he was trying to study while his roommates were partying.
At son's school there was NO accommodation for engineering majors. NCAA baseball players are supposed to have one day a week off, usually Mondays. Son was expected to do as many labs as possible on Mondays. If he couldn't do them on Mondays, he was expected to do them early on Tuesday or Wednesdays. This was not a big problem at his school, but it is at others that have late afternoon or night labs. He was a little late for a few practices, but that was no big deal. If he had a game, he was expected to miss the lab.
Someone commented that these majors may be easier for pitchers. Not necessarily. This was certainly not the case at son's school. Pitchers were generally expected to be at the field before position players. A lot depends on how ambitious and/or anal the pitching (or position) coach is. Son was a pitcher. Sometimes he would pitch on the weekends, but he was still expected to travel to midweek games, even though there was no chance he was going to play. I once suggested that he ask his coach if he could skip a Wednesday trip to study for a test on Thursday. He made it clear that there was no way he was going to ask, and no way the coach would agree.
When son was being recruited we asked all the right questions. One thing we asked was what happens if the team leaves early Thursday morning for a road trip, but son has a test on Thursday or Friday. The academic advisor gave us this story about how in the past he had arranged for tests to be proctored by someone at the school they were visiting. Unfortunately, the advisor had no experience with engineering professors who have little or no experience dealing with athletes, and frankly don't give a rat's behind about the program. Son ended up taking several tests early, before leaving on the road trip. Losing a couple of extra days of study time does not help your grades.
A number of son's engineering classes involved a lot of group work. Arranging to meet with a group of non-athletes around a baseball schedule is not easy, and sometimes impossible. At times he had to make his contribution to the group by phone or e-mail. Frankly, there may have been times when he didn't make a major contribution to some of the projects.
At son's school, most of the engineering students do not finish in 4 years. In some cases, this is because they choose to co-op/intern during one or more semesters. Many kids end up finding jobs this way. Taking a semester off to co-op is out of the question if you play baseball. If you play at a school where players are expected to play summer ball, you will not be able to do summer internships either.
Even kids that do not co-op/intern often have difficulty finishing within four years. Son's school requires a big group project that all engineering students must complete, usually during their senior year. This is virtually impossible to do while playing baseball. My son had to come back for an extra semester, just to do this project.
After four years of college, all of the athletic and/or usual academic scholarships end. When a kid has to go back for an extra semester or year he may end up paying for it himself. HOWEVER, some schools have programs that will pay for the full cost of attendance if a former athlete needs an extra year to graduate. Be sure and ask about this during the recruiting process.
I cannot emphasize enough how important being a good student and/or committed/dedicated can be. Son had a younger teammate who had all three things going for him, bright, great student, and committed. He will graduate with a 3.8 or 3.9. My daughter double majored in Biology and Philosophy. She also rowed for 2.5 years. The time commitment for rowing is close to that required by baseball. Rowing undoubtedly affected her grades to some degree, but unlike my son she is a very good student, so she ended up with a 3.6.
Just a couple of notes about grades. After a couple of years in the minors, my son's team decided it was time for him to become a engineer. He soon found that there are many firms that will not even talk to you without a 3.0. Goofing off that senior year undoubtedly prolonged his job search for awhile. But, everything worked out and he now has a great job with a great multinational company. If your kid goes into engineering he needs to keep those grades up. Just getting through an engineering program while playing baseball is a great accomplishment, but you need to keep that 3.0.
Just a couple of comments about Med School and I'll shut up. Daughter's 3.6 GPA was marginal for med school admission. The guys who interviewed her told her that most of the people they were interviewing had 3.9's and 4.0's. Fortunately, her 37 on the MCAT pulled her through. From what I have seen, I don't think a pre-med type curriculum is nearly as demanding as an engineering major. BUT, grades are more important for med school admission.