Bonding again need advice asap please

I'll be bonding the male bunnies (3 of them) with joey and it starts today. We're putting them in their playpen in the bathroom. Now what should I look out for. I know they chase and nip eachother and hump yes? But how do I know when it's gone too far? Blood and squealing? cry Also do I just put them into the playpen together just like that? Joey has already met them but they were in the playpen and he was outside of it. Just want to know how will I know if it's gone wrong and how long must they stay in the playpen together before moving into the shed (where Joey currently lives)

anyone? It's just I'm going home soon so really need some advice before I do go home.

I'm not an experienced bonder so really just bumping this up for you but many people take the buns on a car journey before starting bonding as the stress helps them come together for comfort.
Make sure everything is neutral.
Definitely separate them if there is bloodshed but be careful you don't get bitten in the process.
Good luck xx