I'm a peer counselor with Nursing Mothers Counsel (Bay Area, CA), and I get this question every once in a while. While it's true that you really don't know how everyone's going to react until you're in the middle of the time away, there are some things you can decide ahead of time.
Since your daughter is over 1, she does NOT need formula. It's recommended that she have whole milk, but you can definitely pump breast milk to leave with your husband in your absence. This will accomplish two things: your daughter will still have your milk while you're gone, and you won't have to introduce a different taste during a potentially stressful situation. If you decide to pump your milk, you can go to http://www.kellymom.com/bf/pumping/milkcalc.html to estimate how much breast milk per day your daughter may drink. It's actually a cool little calculator that's relatively accurate.
I heartily recommend storing in breast milk bags (Gerber, Medela, Lansinoh, etc) because they are easier to keep cold and easier to freeze and thaw if that's what you decide to do. They also take up less space and are WAY easier and quicker to warm. I can heat 2oz of frozen milk in about 2 minutes, depending on the temperature of the water in the cup I'm using. You just put warm-hot water in a cup, and put the bag in the water, and VOILA!
You can also go to http://www.kellymom.com/bf/pumping/milkstorage.html regarding milk storage guidelines, but fresh milk is good in the fridge (or kept cold) for 7-8 days, so you may not even have to freeze it. If you freeze it, it's only good in the fridge for 24 hours after being thawed or 4 hours at room temperature. Depending on what time your husband goes to bed, he could potentially take a bottle of previously thawed milk to bed with him and have it pretty much ready for her 4am snack.
Another thing you need to decide is how long you want to continue to breastfeed. If you'd like to continue indefinitely (or have a certain age you're striving for... say 2), you'll need to stimulate your breasts while you're away. Most women use a pump for efficiency and ease, but you could also hand express. Even if you're ok with your daughter weaning at this point (which may happen after 3 days), you'll need some kind of stimulation to help you avoid engorgement. You can definitely hand express for this purpose.
Regardless of your breastfeeding goal, the milk that you pump/express while you're away can be kept cold in a cooler with ice or a fridge (preferable). If you're flying, this expressed milk will need to be "declared" when you go through security, but breast milk is not included in the 4oz rule.
I second the notion of the cup instead of the bottle if she's never had one before. If she has, stick with what she's familiar with. Maybe even let dad give her a bottle for her bedtime a couple times before you leave or a couple for her first in the morning. You could use this time to pump and store.
If you have any other questions, feel free to email me at ____@____.com, and I'll do my best to answer them. Enjoy your time away, and treasure the time you have with your family :)