Talk about schedules (and then add at least 20% more time to each part of the schedule). Think about Megillah; distributing Mishloach Manos; visiting family, friends and teachers; Purim Seuda; Shabbos preparations; baby’s naps.
Talk about responsibilities – who will do what and when. Getting the kids ready and keeping them happy, Shabbos preps (all the many aspects), preparing the Mishlaoch Manos, preparing and serving and cleaning from Purim Seuda.
Talk about possible obstacles and pitfalls, and how to work with those. Too much sugar. Delays in shul. Purim drinking. Traffic.
With all that, be flexible. And laugh at the mishaps.