[Discussion] Tips for keeping play safe between dogs of different sizes

So my dog park "pack" (group of about 15 owners and their pets who all get along and now organize play dates) has dogs sized from full grown mastiffs down to 4 month old dachshund. All of the dogs get along great and play together no matter the size. I do call my pup off from playing when he's mouthing the small dogs if I feel like he's getting anywhere close to hurting them.

What I'm concerned about is my pup thinking he can't play with them or accidentally hurting them. The small dogs will come and clean his teeth for him and when he does mouth them it's extremely gentle.

So what are your tips to keep them playing safe? I try to read the body language but worry I might miss a sign due to the size difference.