Did this with two adults and 5 year old triplets:
Barnstormer is a firm No because it's only 2 seats per car and no adult to wait with Twin1 while Twin2 rides and vice versa. Because each car is only two seats, there's no wiggle room with that one.
Space Mountain they say the adult must be immediately behind the kid, so you would have an issue there. We did it once where we made a ride friend so that we could all ride in one go with my third in front of a stranger adult. You'd want to be looking for a group of two adults to get into line with, with kiddo then taking the 3rd seat in that car
Buzz Lightyear and Toy Story Mania they'll make you sit three together with only two shooters, so adult doesn't get to play, but you can sit 3 across.
Speedway you can request that each kid gets to drive once. They'll give you a little flag on your first lap to let the attendant know that your kids get to switch seats and go again instead of having to get off
Slinky Dog and Seven Dwarfs they'll let you sit next to one and immediately behind the other, so you have to figure out which of them is willing to be brave and not sit directly next to you. Guardians wasn't open at the time but I'm assuming it's the same because you're able to be in the ride vehicle immediately behind one and next to the other.
Mine didn't want to do Everest, too short for RnR, so not sure there.
Other rides you're fine because they let you sit 3, even if it's a squeeze. I'm wracking my brain to think of other rides where it was an issue but I'm pretty sure everything else you could do the 3 in a row/seat, even if it was tight.