Just a thought, when I was looking for the custody statute in your state I saw that in Illinois you can ask for a right of first refusal. You would have to have this written into your agreement. But basically if she is unable to care for the children because of work, a trip, etc., then she has to give you the option of having them before she brings in a third party (unless an emergency where there was no time to notify).
I think it very likely she will quickly find that it is overwhelming, as I said in my earlier post. Also, if she doesn't derive any pleasure from watching you unhappy about what she is doing (having the kids around others, etc.) then she may well stop doing it.
