Grandpa takes my kids whenever they want also, or comes with us almost every week. We used to take turns driving but I have a bigger enclosed now and can get 6 in my trailer so I usually drive and grandpa will fill the sleds. It honestly doesn't get any better. Not nearly the extreme riding as when just the "boys" go but nothing better than watching your kids learn to love the sport you love.
sounds like my dad and i. until 3 years ago we used his truck and trailer every ride. i was finally able to get my own trailer so now i drive. it was weird for my dad to get used to; i pick him up and the sleds and truck and gassed up and ready to go. he mentions that he feels bad but i figured he covered it for the last 25 years the next 25 can be on me!
as far as others go most guys throw a 20 out for the truck. the truck usually takes 100-120 so it doesn't even cover fuel but i figure it better than nothing haha
If im taking younger guys so far they've all offered to pitch in; i usually dont take their money since i know what it was like trying to ride out of high school.