A friend gave me seventeen 8oz Dr. Brown bottles. How many 4oz bottles should I register for, though?

Here's my feeding/childcare situation:
0-3mo: Hopefully mostly breastfed; maybe a bottle here and there
4-5mo: Childcare for 9 hours a day, 5 days a week, hopefully all pumped BM
6-7mo: Home again with me, hopefully mostly breastfed; maybe a bottle here and there, starting to try solids,
7mo and on: Childcare for 9 hours a day, 5 days a week, hopefully all pumped BM but want to start moving more to solids because pumping as a teacher is going to get complicated.