I wish our 20 yr old son was more committed to saving than spending!!!! He is in the military and hasn't saved a single dime since he enlisted over a year ago . . . I digress :)
You are a smart cookie and your job (if I remember right) is in finances so it would seem natural to help your child out. However, I really, really think that he needs to sit down with his own financial planner, of his choosing, without you. If he wants to bring a specific item to you for your opinion, great. But it sounds like he has his big boy pants on and as a parent, it is difficult to separate out what WE think is best and what is actually best (sometimes the same thing, sometimes not). Plus, if he felt steered in a wrong direction by you at a later time, that could hurt your personal relationship - never a good thing.
Additionally, I abhor the idea of a parent putting money away for an adult child - for two reasons. One is the obvious - if you are capable of earning, you are capable of saving and this is a lifelong skill that needs to be learned. Second, is you have NO idea what the future holds for you. You could be struck down with a terrible disease tomorrow forcing you to file bankruptcy or need financial help from a source that considers your assets and income. You cannot just transfer this mythical $50k that you have been saving for your son on his behalf back to him and then move forward like it never happened. Doesn't work that way at all. In bankruptcy, the look back periods are 1 year, 2 years, 4 years, and 10 years - depending on the type of transfer. I know you are thinking that this will never happen to you. So did many, many of my clients . . .
Yes, him having financial savings would likely impede him from getting student aid/work study/deferred interest, but likely he wouldn't qualify for any of those anyways as soon as he shows them his tax returns. Pretty much everybody qualifies for regular student loans with regular interest and repayment terms. He just isn't going to get anything for "free" with his projected savings - and likely wouldn't even if you were holding on to them for him.
I think that this should be on him, with minimal guidance from you. This probably isn't going to be a popular opinion either, but I also think that he should be looking at moving out of mom's house and into his own place - whether it be a condo he is financing or with 3 other guys in an apartment. There is a great deal to be learned when you are living on your own - he is in a great position to do that right now and I think I would be steering him in that direction.
Good luck!