Those first personal emails are such a rush for your son and the family, but they are a double edged sword. First they indicate that your son is on some kind of list and they are interested. Congrats, this is good.
Now the reality, and the hard part. You son is likely one of many who is on their list and you really never know where until you get further along in the process and get to the point of an offer, or where he can ask "where am I on your recruiting board for my position? number 1, 10 , 50 ?" Keep filtering through the emails, filling out the questionnaires. It is an extremely exciting and stressful time.
Good Luck!
To add onto BOF I think some of this contact can be a trap. I have seen it with my son's 2016 peers. Lots of initial interest last fall for a couple of boys from big time schools. Everyone expecting that interest to continue through spring and summer this year.
It didn't and I had one dad admit that now he is really concerned because based on this interest they stopped doing some of the legwork and now felt like they are behind. To top it off his son is now injured and going to miss the fall.
Regardless of what you get and who you have talked to I think the best advice consistently given to here is to keep working everything up and until your son finds where he needs to be. Good luck to everyone.