I think you not changing your plans based on her last-minute changes would have been better. This is the reality of a separation - you have to figure out your work/life balance without counting on the LBS.
She took that client because she knew that you'd probably cover for her.
I am all for spending extra time with the kids and would love more, but not at the expense of my W not meeting her responsibilities.
Your W needs to realize she can't just take last minute clients now and that the kids schedule comes first. If that hurts her paycheck, too bad - this is the reality now.
I can see this as okay if you also need her to spot you at times. If that's not the case, then don't let her change up her schedule around at your expense.
