My ds1 has hypermobility and hypotonia and so was delayed with his gross motor skills. Gym class at the local sports centre was fantastic for him and a great help for when he started school, because it meant he wasn't obviously behind in PE lessons. It wasn't the sort of gymnastics that puts much in the way of strain on the joints in the early years: just lots of bunny hopping, forward rolls, balancing, running, skipping, hopping, slithering like snakes, donkey kicks, copying the teachers' movements, playing on gym equipment, etc. It didn't start to get more serious until he had to move into the school-age, 5-7 year olds' class. After a couple of terms of that, they were beginning to do things that alarmed me a little bit, because of his hypermobility (eg swinging from bars, which is one thing we were advised not to let him do, in case he dislocated his shoulders). He also started to notice he found things difficult that other children didn't (eg skipping with a rope!...).
The feeling he was behind his peers wasn't an issue in the 3-5 year olds' gym class, because of the way it was structured, and because there was quite a good age range of children, so different abilities were expected, plus little children just don't compare themselves to each other in the way older children do. He certainly loved it, and wasn't phased by the fact that when he started, he couldn't hop, skip, run very fast, do forward rolls, etc. So I would very much recommend it.