M.A.
C.,
So glad you posted this. These are great questions, and I happen to have some great links with really pertinent information about this. I've also been pumping for my daughter in daycare since she was about 3 months, so that makes it 18 months that I pumped! We are still nursing very successfully at home, so this strategy is not only backed up by good info that I'll post, but by my own experience! Also, I lead my offices Lactation/Pumping support group, so I've got tons of good info that I'm VERY happy to share with other working moms.
1 - How much milk does my baby need? Your baby needs about 1 oz/hr when she's away from you. For a breastfed baby, this amount NEVER EVER changes. Breastmilk intake is NEVER based on the age/weight calculations that formula is. It's different. Here's more info: http://www.kellymom.com/bf/pumping/milkcalc.html
So from 7-3 would be about 8 oz (this would give you some leftover in case of emergency). It's best to spread them into smaller bottles. If you nurse around 6 AM or so, you'd give at around 9 AM, then 12 PM, then you'd nurse at 3. That's just an example. Because you're giving solids, things will look a little different than that.
The most important thing to remember when feeding solids to a baby, that their primary source of food should be breastmilk or formula for the first 12 months of life. This is based on the reccomendations of the WHO and the AAP. This means, you should not decrease the amount of milk you send to daycare during the first year of life. Here's some info on that: http://www.kellymom.com/nutrition/solids/solids-how.html#.... Remember, breastmilk has more fat and nutrients than any other food, so reducing milk with solids will not only cause your supply to drop, but it could affect your child's weight gain and growth. That's something that's really important to remember and it's why the WHO and AAP come out so strongly on this. Solids at this age are for play and learning, and aren't intended to be a really steady source of nutrients.
So how do you balance solids and breastmilk? Here are some sample menus to help you get started. These were so, so helpful to me: http://www.mother-2-mother.com/samplemenus.htm
Also, on the pumping, I've been pumping for so, so long. There are some things that make it easier, but I'm worried that I'm writing a novel, so I'll message it to you. Hopefully that's okay. In the mean time, and for anyone reading this who is in the same situation as you, here is a link to a list of pumping tips specifically for teachers! Hopefully this will help you: http://forum.kellymom.net/showthread.php?t=86861
If you have any questions about this info, please let me know.