I love how mature and thoughtful your son is being in the face of grief. Kudos to some great parenting, right there :)
I am trying to think of things I would want to chat with my parents about or get their advice/commiseration/information.
what I would want to know:
--my blood type, family health history, etc, things that would be good to reference down the road
--family stories of older relatives. Any immigrants or entrepreneurs or just cool people doing cool things? I was really surprised at how much I didn't know about my grandparents until after they had passed and finally the stories of their early lives started coming out. It would have been so great to know all these cool things while they were still alive!
--how to recover from a mistake at work or hurting someone you love or just generally being a toad (it happens to the best of us). How to pull yourself out of the rage-shame cycle, empathize, and properly apologize and make amends.
--How to/tips for going on a proper date
--how to clean/do common chores and things to consider (laundry (how to read tags, detergent types, etc), dishes (what can go in the dishwasher and what can't, watch for knives), cleaning toilets, cleaning stoves, trapping/killing pests, etc)
--basic how tos for things like setting up doctor appointments (plus an explanation of insurance???), filling a prescription, opening a new bank account, etc. These things were completely mystifying to me.
--advice for job searching (and knowing when a job isnt a good fit). Resumes, interviews, basic job advice (time mgmt techniques, meeting etiquette, etc) and graceful transitions/don't burn any bridges. What to look for in a leader/manager.
--under what conditions is buying a home a good idea? And IF it is, how to do it.
--basic car maintenance guide, like when to change the oil and the contact info of a mechanic you trust.
--tips for calming anxiety. Exercise, deep breathing, happy place, and emdr cross-body tapping.
--how to throw a party (what to consider, what kinds of foods are best/easiest, time management for setting up, etc)
--how to pick up/hold a baby and change a diaper