'I just wanted to remind you of a few days that i have family obligations and you previously said it was ok for the kids to join me. June 24th and July 6th. Both are your days, would you like to switch days, or what would you like to do?'
What would be a good response indicating I am really ok with whatever she wants to do?
First you need to figure out what you want.
Do you want the kids? If so, then propose days you want back.
Shes asking what you want. Dont act like you dont care. Its your parenting time!
"Thats fine. Is it OK if I take XXX and YYY?" Dont just pick days randomly. Think of what days are good for you AND your kids based on your schedule with them.