Not all dogs are appropriate play friends, particularly whilst they are still growing and learning. For example, putting a 6 month old Cavoodle in to play with a group of 6 month old Labs, Boxers and Staffy pups, is like putting a 7 year boy into a game of AFL with 18 year olds. He is going to get hurt and not like the game. The bigger, heavier, bouncy pups do not mean any harm but they will overwhelm lighter smaller pups simply with their energy and size.
Parents of the larger heavier pups need to take them to play with the dogs and pups that can handle their energy and weight and are capable of teaching them. If you have a light weight smaller puppy choose the larger calm older doggies to build little ones confidence around bigger dogs, not high energy large dogs that will overwhelm and sometimes frighten them.
If you have a large breed energetic pup, when they first get to the doggie park, they’re at the top of the play pyramid, there’s only a few doggies that can tolerate their energy and play, so take them to play with those doggies and as their energy is drained their pyramid opens up and their play options increase. When they’re completely exhausted they’re a lot more capable of playing appropriately with smaller less energetic doggies.