I read your response yesterday and thought you did a good job, when I read it again today I think I would change some things in future exchanges.
"I understand it is easier and more comfortable to arrange the schedule with your parents instead of me."
This to me sounds like you know she doesn't want to or that you are difficult to deal with. Don't put negative thoughts in her head that she may or may not have.
How about keeping it simple.
"Happy Monday. I have zero problem with them staying overnight with your parents this time. In the future if I could have the opportunity to keep them first per our agreement I would appreciate it.
Enjoy out west and have a safe trip."
Or something along those lines, maybe somebody who has more experience with this can offer some advice.
Me-44 (45) H- 50 (51) M-'96
S-18(20)D-15(17)D-12(14)
BD Feb 2014 (he works overseas) home Oct(sep rooms) (EAs possible Pa's unconfirmed) insists wants D through July 2015 no more talk of D since