My DS is very not picky. We started with DP giving him the bottles, but now I can as well. I think we started with 1 or 2 oz at around 6 weeks. I don't remember starting to pump until the 7th week, and I returned to work after 8 weeks. Most of what I pumped prior to my return was put in the freezer and eventually donated because I was able to pump so much. Kellymom has a good rule of thumb on her page about how much they will eat. I think it's 1 - 1.5 oz for every hour you are gone? Make sure you trust your daycare provider to not soothe with the bottle because they will be the ones telling you if you need more milk or not. My DS has been at 17 oz for a 10 hr day since about 4 months old.
eta - I just realized that may have sounded snide about DS not being picky. I didn't mean it to be!