Erm. Probably help him correctly set up a software wallet on his phone then send him a certain amount of bitcoin. Not sure why DOGE is an option, knowing that Bitcoin's fees right now isn't even high.
if he is a beginner, and he obviously is, I am not sure how good it is for him to start with any phone wallet. Many things can go wrong there, just out of ignorance.
I worked as an internet provider reseller, and in general, most "beginners" do not have a clear idea of what online privacy means, or the importance of passwords/private keys.
^Of course, if gramps is planning on allocating a decent amount of money to bitcoin/crypto, then probably buy him a Ledger/Trezor.
Hardware wallets are probably the best starting point for everyone who is just starting to learn about crypto and wants to invest.