I’m 6’4” (mostly legs) so I know the struggle of leg room. To give you perspective, economy seats on planes are usually difficult for me to sit in for more than a few hours.
As for ride difficulties, 7DMT I am not too comfortable in but given it’s a short ride, I’m okay. Just have to hope the ride doesn’t stop or I’m stuck at unload for too long.
BTMRR can be a bit tight with my knees pressed against the front of the row but again doable. Same can be said for Pirates with my knees almost up against my chest.
Regardless, there are no rides I “can’t” do because of my height/legs. So I would recommend your sons try every ride and if they are uncomfortable, it’s only at most a several minute ride. Heck, they are young (I’m 26 as well) so they still have flexibility and no aches and pains (yet!)
Enjoy your family trip!