There is an excellent solution to both of these - if your son wants it - chemical engineering is indeed hard graft and I would strongly argue that you DO need a social life to get through it not to mention that University is a great place to be sociable, build up networks and learn how to live and be yourself.
I would guess that working in Pizza Hut is very grounding, and allows a very welcome relief from head work. BUT another option is the one he is working towards already i.e a paid placement over the summer, either with an academic group at the same university (note; with a Chemical Engineering degree this could be outside his faculty too - and academics love personal contact and students who they can trust to be enthusisatic) or at another university (tap known academics for collaborator contacts that they want to form closer links with - supplying a good enthusisatic student to a collaborator is a great way to build links) or a placement with a company.
If you want to help, suggest he contacts department secretaries for the nod if any employer placements arrive. Usually they are extremely helpful. Also the University Careers people may have contacts here too, and again academics who have industry funding are often very keen to get students they know into companies they work for.
I would be very proud of him - he is clearly thinking like a top-rated student as less than 1% of students think seriously about trying to get a placement, and that is one of the strongest things you can have on your CV in terms of getting later employment, but more significantly in terms of obtaining funding for a PhD course.
Funded placements (even unfunded ones) show a) an academic or industry has selected you and taken a financial risk with you (i.e it is equivalent to a 'Prize for outstanding work' when it comes to PhD applications) b) a clear interest in the subject and will c) give him a much better insight into uses of his degree, academic or industrial research and d) will vastly improve his maturity and grades (I worked at a University once, and ALL the students who had been on placement saw a grade increase, usually to a first, just because of the wider vision, discipline and maturity they gain.
Encourage the placement, don't worry about the Pizza Hut too much - he sounds like he is pushing in the right directions - not to mention that I bet Pizza Hut gives him more access to women than a Chem Eng degree does!