I like building sand castles. I also like reading Dr. Seuss books and similar ones (like P.D. Eastman's Go Dog Go.) I like some kids movies, though most of the ones I like have double entendres intended for adults (i.e the vast majority of Disney movies, as well anything by Looney Tunes). On a similar note, I like Sesame Street episodes from the 70s and early 80s (watching more recent Sesame Streets I realized the neighborhood's changed to much, and OMFG is Elmo annoying!)
I don't think teetotaling is immature, but in my experience it is horrible. If I had more regular access to cannabis, I might smoke that more and drink alcohol less, as it seems to have somewhat fewer side effects. But, in any case, a life without regular use of some mind altering substance is not a life I want to live.