First of all, if he goes Ivy he probably won't get anything athletic, as to my understanding they don't pay anything athletic. Maybe other financial aid, but not athletic scholarships.
But more to the point of your question: I don't think there is any standard. Each coaching staff has their own approach to how they allocate dollars. Making matters more confusing, the NCAA is imposing a floor of 1/3 aid for anyone getting baseball money starting with the 2008's. So you won't see kids getting 10% of 20% or "book money" any more. This may free up more money for the stud guys to fight over. I don't know for sure how it will shake out, but I can say that this is all in flux right now, so there are no solid guidelines anyone can give you for what you'll see.
You have to talk to the schools that interest you and see what they are offering. In the end, it doesn't matter what someone else might be getting. All that matters is what choices you have before you.
In answer to another point above: public university programs can do more for you than privates. That's because the dollars they have to spend are determined as 11.7 times the AVERAGE cost of attending. They can milk that to more than 11.7 scholarships if they focus on in-state prospects, who cost less than the average. If you're in GA, FL or TX, where there are "Hope Scholarships" and the like, it gets even more skewed. In turn, those schools can often offer the stud player a higher % because they have more left in their budget to spend.
At a private school, the AVERAGE cost of attending is the same as the cost you face, whether you're in-state or out-of-state. So if you take each player's fraction and sum them all up, you get no more than 11.7. Whereas with a public U., the fractional shares may well sum to more than 11.7.
But sometimes there are other considerations that make you choose the private U. anyway!