Guests not being truthful

Can you give me some advice as I’m very new to this. 

I’ve had guests arrive today & despite telling me it was only 6 adults, they have at least 2 toddlers with them as well.

I’m annoyed that they’ve not been honest with me. 
I’ve had concerns about them too as they’ve asked if they “can make fire outside”. English is obviously not their first language, but we have a very nice, well looked after caravan & I’m concerned they will ignore the rules and get a campfire going. 

Thankfully it’s only a 3 night booking, but I’m just feeling a bit wary that they’ve lied to us already. 
I am on the same site as them so will be keeping an eye on the outside when I can. 

What procedures are in place through this site for guests who aren’t honest?