Hey! sounds like he found my missing wallet
Jeff. How mobile and flexible is your dad? Unless you go for a short tube refractor then anything over about 800-900mm long will put him in some pretty uncomfortable positions. Especially when looking straight up, You have to get get down pretty low. A newt on an eq mount can be just as painful in the neck, depending on which way the scope is pointing.
A dob would be much easier on his back and neck. But if he has a spring loaded wallet, maybe think of a fork mounted SCT scope with goto.
8" or 10" LX90 springs to mind, though an ETX might be more within his price range.