Taking some of my kids friends along.... cannot see a release on line for their parents to sign.. can I just sign the release?

Yes you must go sign the release and then you could leave if you want too.

Depends on if you're fine assuming legal liability for them in place of their parents. If you're taking care of them without their parents, I would hope the answer to that is yes

Not sure, call them to be 100% sure.

Yes

Yes, just be safe and have fun