You may also want to conciser getting "Right of first refusal" written in. That way, the other parent should be offered the oppertunity to watch the kids instead of a baby sitter. (or over involved grandparents).
Yes like the idea of a Right of First Refusal. I am also thinking about splitting holiday days in half as we will be living within 10 minutes of each other. No need to miss out on a holiday when we are that close, and in our history we have never done anywhere near a full day and evening (15 hrs!) anywhere for a holiday, so shouldn't be a problem. Lots of details to still figure out. My L says get an agreement that is as detailed as possible so there will not be too many constant decisions to make on the fly. We can always agree to one-off deviations or outright changes down the road if something is not working.