How do you handle gifts you provide for your kids' friends parties?

We are still not divorced. It is contentious and the less contact and interaction the better. I proposed we split all kid expenses 50/50 while working through divorce documents. I created spreadsheets for each month and included things like gas for our college age daughters car, tutoring, sports fees, co-pays and I also added birthday party gifts. Our younger child (age 9) attended 5 parties in the last few months and I ended up purchasing the gifts for all parties. The generally all fall on my parenting time due to the way our schedule works but she goes to her dad's each week. She specifically mentioned that she wanted her dad to take her to get the gift for one party but when I picked her up a couple of days before the event they had not purchased anything. I spent about $100 for the 5 gifts but didn't want her to not be able to pick something she felt a friend would enjoy. I don't want to be responsible for telling him when to buy a gift and ensuring he does but I do not want to shoulder the coast alone. I always add the birthday parties to the shared kid calendar I created.

He feels it was inappropriate for me to put that on the spreadsheet. How have you addressed this?