OD- I'd lose the part about the boys presents. I can tell it irritates you - but it won't get you anywhere.
The meat is in the second paragraph. This is just my opinion - but I would open by pointing out that you only get to see the boys X days a month, that time is important to you, and that this weekend's events have made you realize that she is not on the same page. Therefore, in order to avoid any future misunderstandings - your position is that from X time on Friday to X time on Sundays is your time (with respect to the boys wishes ). Of course you will be happy to be flexible if possible, as long as it is discussed ahead of time.
