I agree with the other post, I would start give him bottles in between meals instead of with them.
At 6 mos I was only sending 3 maybe 4 bottles with her to the sitter, I would also send a jar of breakfast food, a jar of food for lunch, and some kind of snack (ie: puffs, crackers, or cherrios) that the babysitter could give them to her in the afternoon. I would nurse her before she went to the sitters, then She would get a bottle in the morning around 8, then one in the afternoon after lunch before her nap, then one right before we picked her up. I would nurse one or two times when I would get home from work before bed.
You may want to work on cutting one of his bottles out during the day by increasing the amount of food he eats. Eventually he will work his way down to eating a bottle in the morning one in the after noon then one before bed. I found with my three gradually removing bottles from their day helped, so that by their first birthday I could completely get rid of the bottle and move them to milk.
I am sure the day care will try and work with your schedule, I would have a meeting with his teachers and ask. Hope this helps.