Yes, there was a trust fund that gave J.R., Bobby, Ray, and Gary 10 million each, and Lucy $5 million, Funds immediately accessible to each except for Gary, who was restricted to the interest for 4 years. It made sense in-character, that Jock would be worried that the sudden influx of money would lead to Gary wasting it, possibly due to alcohol, so this was his way of trying to save him for his own good. Perhaps hoping that the 4 year limit would give Gary time to, I guess, get used to the idea that he was going to be rich. But I'm also thinking this was mostly done as not to disrupt the current status quo on Knots Landing, as the writers weren't planning for Gary to suddenly have all that money, so this way it kept things "normal" for a while?
It was mentioned that there was a separate trust fund for other grandchildren, but it didn't say how much money was in the fund, Just that it would be divisible equally by however many grandchildren there were at the time and they'd each get their share when they turned 21. At the time that was just John Ross and Christopher, but by the time they show ended that would have included at least Margaret and Lucas (with the dream season split, we don't know if Gary had children, J.R.'s son with Cally wouldn't be included since he kept his existence secret, but I believe James could have had a legal claim on some of that inheritance if he'd chosen to go after it).
So we know they got something when they turned 21, but not how much. Christopher is the one who, if we go by the original series, should have independently wealthy by the time Dallas TNT began, as he would have inherited Pam's shares in Wentworth Industries in addition to whatever he got from Jock.