That sounds fine. (And you can tell that she is sounding annoyed by the fact that you will not change your plans to accommodate her activities.)
Good for you.
"Make you pay?" by getting angry at you? It's hard to do, but just ignore this. She can't hurt you more than she has already.
Stick to the facts, be reasonable, but don't be afraid to ask for what YOU want. You get a voice too. If you want to take them out to dinner when they're with her, make that one of your conditions.
I wish you could stop worrying about "upsetting her". She's clearly not concerned about upsetting you.
If you're calm and civil, if she's upset with that, it's not your fault.
Me 54 Him 63 M 23 T 29 0 Kids Funny Farm of Rescues 12/12 OW-- 5/13 ILYBINILWY: A denied 9/13 Proof OW: ENDED 2/14 Got D papers on my BD I kicked him out for my sanity 9/14 He wants to "talk"?