Hi J.,
My son started daycare when he was 4 months old and we were in the same situation. I was breastfeeding but could not get him to take a bottle from me or my husband (with pumped milk or formula). We tried and tried, and I was getting so stressed out with daycare looming on the horizon. I tried different bottles and different nipples. I tried leaving the house so my husband would offer a bottle without me being around. We tried waiting until he was pretty hungry, but that usually just pissed him off and that didn't help. I eventually decided that I would just keep offering a bottle to him, when he was in a good mood. Usually he would chew on the nipple more than anything. Sometimes he might suck a little. I figured I woud at least expose him to a bottle and then when he was offered it at daycare it wouldn't be totally foreign.
Going to daycare was the trick. I think him being with other women who had done this before and were confident really helped. They would offer him the bottle, never letting him get upset. They just kept trying and trying. If he became real upset they would stop and walk around, calm him down, and then they would try again. It took them about an hour and a half. I guess he was hungry enough and they were persistent enough that he took it. And we've never looked back since. It still took a while for him to take a bottle from me thought(a month or so). It did turn out that he wouldn't take breast-milk from the bottle. They found he would get really upset if you offered him a bottle with breast-milk, but would be just fine if it was formula. I think it just had to be totally different for him.
We ended up using playtex drop-ins with natural latch, slow flow, latex nipples. On a side note, at that age, he still slept while being swaddled, and the daycare ladies actually decided to swaddle him up when they first fed him. I guess it helped him feel cozy while eating.
I hope this helps. All I can say is that he'll be ok and he will figure it out. It might take a little time, but the ladies at daycare have usually done this before, and are usually confident and persistent enough. Sometimes being in a different environment and not having you around can help.
Good luck!
K.