Hopefully the 2 of you can have what my ex-husband and I have with our daughter. We work with each other and she has always come first.
However, my husband's ex-wife would never let that happen. We have sole custody of the kids where she has no more visitation and have spend over $100k in the last 4 years to do so out of complete necessity. However, our situation is so unbelievably in the minority it's not even funny and hopefully nowhere near your situation!
My ex husband and I made a pact before we divorced. We said that our daughter will always come first and we will not remarry someone who doesn't understand that. His wife is now a friend, and we have all vacationed together. It may sound odd to some, but we just go with the flow. They both come to my parents house for holidays and even went on our first annual family reunion this year with us.
If they are going out of town to my daughter's stepmom's family for Christmas and want her to go, she goes. If I want her to come with me somewhere, she comes and we just work it out.
I know it sounds impossible, and my ex-husband is a REALLY nice guy, but it is what is best for us and our daughter to be friends. She sometimes hates it because she cannot pull ANYTHING over on us!
As for holidays just don't get wrapped up in quantity of time. Make the time quality and never, ever put your kids in the middle of anything. Never say anything where they can hear, even in passing such as "we would but your dad... fill in the blank." My stepdaughter's mom made them spies and asked them question after question and blamed my husband for everything. It really messes kids up. Not saying you will do this, because it sounds like you two have things worked out and are going to do fine!
Good luck, and I wish you the best. Divorce is so hard!