They have nothing to worry about. My sister and I are larger than that (we are short, so we carry around the middle). We can fit on everything we ever tried. We don't do RNR but I understand that shouldn't be a problem. On ToT, if we aren't with our skinny family members to put between us, we ask to leave a seat between us because it's bit challenging to get the seat belts latched when we're beside each other. There's no problem latching when we have a bit more space - the seat belt is long enough, just tell them to pull it all the way out before they sit down, works every time. We do this every time there is a seat belt
I do all the other coasters with no trouble at all. Space Mountain looks intimidating getting in, but they'll fit. Getting out isn't too graceful, but the best thing to do is push up with your legs and arms until you can put your butt on top of the seat back, then stand up in the seat and then out of the vehicle.
7D was the only one we said we shouldn't have done together. If we rode in our own car there would have been no problem.
Dinosaur could be a bit uncomfortable if they carry their weight in their hips and thighs because of the hand grips digging in, but I found if I braced my feet on the floor it helped with the jarring.
Some of the attractions still have turnstiles. Some we could fit through, some not. Tell them, when in doubt, ask the CM to go through the gate. They are great with any accommodation like that. I have not had a single issue with any request we've made. (Including a "seat between" or separate cars) They always make us feel very welcome. We love Disney World!
