Anonymous wrote:With a 2 year old at home, I'm surprised your pool is so easily accessible
Be careful OP. Do you know the regulations for your pool in your county? Under your insurance policy? Often both require that a pool be completely fenced in. It depends on the size of the pool and where you live but you don't want to risk anything happening to one of the kids.
That said, I'd speak nicely to the parents about it before you get any more frustrated. Something along the lines of "you're kids are great and we'd like to have them over when we invite them but we have to ask that you make sure they don't come over uninvited. As you know, we have a pool and that necessitates some strict rules regarding access."