I am a Beaver leader (Beaver Team Lead) and I think your questions have been answered. But I'm still gonba put my bit in lol.
Your group will have a risk assessment that you can view - just ask - they won't (or shouldn't) be offered. I certainly wouldn't.
Every venue will have a different process.
We have a field gate. We close it about 15 mins after arrival time to discourage anyone who's not supposed to be tgere from coming in. We don't lock it as we need access for emergency vehicles.
Kids are "signed" in. That means the adult is acknowledged by the adult taking the register and knows we know their child has arrived.
Its not always me doing the registration, im often answering questions whilst another adult does it and someone else might be setting up.
Kids have to "ask" to go to the toilet, but only so we know who is where, and can check they aren't too long.
On leaving an adult must collect the child & one of the adults has to have seen them - ie, I have Fred. Fab, ok, see you next week. I also ask parents to let me know if someone different is picking them up, just so we know - a few parents take turns bringing & picking up multiple kids.
Again, can be one of 3 or 4 of the team as I might be talking to a parent about the session etc but as long as I can say oh Bella, did you see Oscar leave...yes, grandma came for him. Thats fine, they are accounted for.
We don't lock the entrance so we can exit quick in an emergency...but that might change if I have a Beaver who is a high flight risk.
Sometimes it looks like chaos to a new parent, but once they have helped a few times, they realise we have processes in place that work and the chaos is organised lol.
Now, a meeting in a park or an outing, my head counts are frequent and we always take extra helpers - just for eyes on the kids.
Also, get involved and help, even if you start as door watch, they might actually need that support if they have some over enthusiastic kids, but they don't have anyone to do it.
You will find yourself helping the sessions before you know it though.
You don't need a DBS for once or twice a term as an occasional helper, but more than twice a month, your a regular helper. The group will do your DBS for you, no cost to you.