For Dad, books on tape and a tape player with big buttons. * He may be fine with CDs, but most older folks are more comfortable with tapes. Or any device which can download and play audio books and NPR-type stuff. (Hopefully a more informed person can elaborate.)
For the boys - how religious? Like, no Santa Claus-religious? Take away super hero toys because they compete with the omnipotence of God-religious? If it doesn’t mention _name of diety here it’s evil-religious? What religion?
In general, most fundamentalists will not argue with anything that has to do with survival skills building, and most young boys are into camping. Maybe ropes and a knot tying book, or other woodscraft related things? A pup tent and flashlights. . .
If their parents are not anti-graven-images types then a sketch pad, how-to-draw book and art supplies would give them an outlet.
Kazoos, harmonicas, recorders and guitars can also provide outlet for tightly bound children. Include a book of camp songs from the religious store to aid parental acceptance. Even an electric keyboard can be bought fairly inexpensively these days.
*Or, what Missy said, LOL!