Depends on his degree as to whether he can work or not.
I was an engineering student with 37 hours a week of lectures (including labs) in the first year.It dropped off to about 20-25 hours a week in year 2 and 3, but there was still a lot of time outside uni taken up in projects, assignments, coursework and revision in all 3 years. I also played sport for university at BUSA Div I level and a bit for my club/county so there were practices for those things and matches on top of that. He may have to make a decision if he plays any sport about how seriously he wants to take it.
I didn't work part time in my first year at term-time, but I worked two jobs, sometimes 3 during the holidays in my final year. My parents paid my first term's accommodation and that was it. I was not eligible for a loan either, so it was pretty hard going.
My relatives would see me once or twice a term and give me a few quid here and there, and take me out for dinner and so on. It really helped that I was in a catered hall too. I don't know if I could have managed it self catered in the first year.
I'd like to think I'd have done better academically and sports wise in my first year if I'd been better funded. It was gutting to see other students in my halls and on the team spend money like it was going out of fashion. They were good folk, but it's hard to stomach when you're taking a fiver out of your overdraft for a night out and some kids are planning skiing weekends and holidays. Dropout rate in engineering after the first year was crazy as well. The effort I had to put in meant I saw my degree through to the end too.
I'd suggest a compromise. Instead of cash, say you pay for a fortnightly supermarket shop. If he rides, or plays sport, say you pay for consumables, or kit.
Of course, this all depends on how good your child already is at managing money and self control on the booze.