always ask older relatives first - so get ds to ask you, his df and then any d grandparents next
Have you got ds birth certificate? Show him this and explian that they have been issuing these certificates since 837 and as it gives mothers and fathers name it is really useful when researching family history.
if you are married can you show him a copy of the certificate, it shows the fathers nmaes and this helps wihth research, along with ages of bride and groom adn fathers and grooms occupations (brides often didn't have one)
I would leave things like genes reunited alone at his age esp - go to rootschat and get him to get help there - it is a very weel moderated board and they will give him help and advice to get him started once he has the basics from his oral information from his nan etc.
You may well have to buy a couple of certificates ie 7 each to get back before 1901
Try the site www.familysearch.org, they have loads of info. Make sure you double check everything though, as they can get a bit erratic once you go further back. And be careful: I have found making my familiytree extremely addictive ! Also found that I do not seem to have very many interesting people on my side, whilst dh has a knight of the garter, a landlord with houses on wall street, a merchant who died of cholera in riga etc.