Had to be the old "Kicking the bear in the ice-hole joke". Pretty tame on the surface, but a primer sanctioned by the patriarch which lead to a more colorful dinnertime conversation. Defineitly my dad's all time fave. Another was the "Wish you had 2 hats cause I'd like to shit in one of them", but I forget the particulars on that one.
Anyhoo..This just comes from family based dinner chat recall ca. mid to late 60's. Probably some earlier filth noted, but not accepted nor framed in the nuclear family settings which is the benchmark I generally use as a guide to foulmouthedness in tx or rx.

Thanksgiving is a great time to introduce joke telling to the younger crowd...but a planned path is recommended or one can surely piss off the parents. I have used the ice hole joke around the 8 to 10 year old ones with not so much parental browbeating to date and still consider it to be a safe bet.

It's alway good to hear a kid deliver a joke. I will always laugh somehow.
Anyhoo...Enjoy your fam this year...YMMV,
rot