Congratulations!
I suggest reading the whole thread from the link that Anotherparent provided. In addition to that list, you'll find some good debate about what to ask as well as what not to ask. That particular list is, as Anotherparent hints, ridiculously extensive but can serve as somewhat of a menu to choose from and can spark the thought process, depending on which apply to you and your son.
Bottom line - parents need to come away with the information they need to be comfortable with supporting the decision and committing to whatever their contributions might be. The player needs to come away with the information they need to make an informed decision to accept the offer or not (not necessarily right away). What is most important is unique to each person.
To the extent not yet known, consider exploring fit, culture, offer details, housing, academic support, player development, nutrition, medical access, etc.