first I would put a pull up on the kid during nap and that solves that problem. second I would tell those parents that change is a part of life and they have to adjust. its a daycare ...kids will come and go ....but that doesn't give the child a free pass with their behaviour. at almost three she should know better then to take toys and I would put her at the table locked in a booster seat with a few toys, a puzzle, or crayons and paper and she can earn the right to get down and play with the other kids. one infraction and back you go.
my first year operating I had one full time boy and a part time girl and an after school child.....at the end of the first year the part time girl left and I got a lot of interest from my ads and filled the rest of my spots and all of a sudden the full time boy turned into a hellion. the parents pulled the same "its cause you got more kids and he doesn't get the attention any more " crap on me ....so I told them that that's life and the sooner he comes to terms with it the better off he'll be. but these parents were so busy making sure this kid was never disappointed, they never used the word no, they spent all their time with him playing and engaging him ....he had no idea that you had to wait for things, take turns, and that he wasn't the center of the universe. if he wanted to go outside they went out side, if he woke up at 4 in the morning and wanted to watch tv they got up and watched tv. when it was time to go home from daycare and he didn't want to go she stood there and waited....but this is not reality and parents today are to busy trying to be their kids friends instead of there parents.
if these parents are intent on blaming you for their childs behaviour problems and peeing while she sleeps because you added more children to your day care maybe its time to replace that family. I am more inclined to believe the chaos at home is the real issue.