The best thing you can do, don't give him, or let the others have toys when they play together. Toy guarding is a serious issue, there are a few ways to stop it. However I advise you to seek a professional behavioural specialist. That way they can help you see signs and warnings, learn to correct them.
As I said, until you seek help from someone in real life, don't let him play with toys if other dogs are around.
I can't let Okami have antlers/bones around other dogs... she guards them. She also water guards, so at the dog park I have to play water goalie while she drinks... it is ridiculous, I know. It keeps her and everybody else safe though. She has never acted badly, she just growls, which is my warning sign to correct/take away.