Hi M., Please take a deep breath, all will be OK. I understand after reading a response from your first post why you are starting to stress, but don't it will be OK. First it is only February; you have 4 good months before your trip, good for you planning so early. First I just wanted to say our dr told us that baby's need formula or breast milk up to 12 months, after that cow’s milk is good, so your first plan is right on target, he will be 12 months so a normal time to make the switch to cow milk. I did things completely different between my two girls, but either way worked. With my 1st I gave her cow milk at her 1st birthday party, and never turned back... with my second it took a little longer as it took her a good month to start liking the taste of the cow's milk, so we continue to supplement one bottle at night just to make sure she was getting enough nutrition.
Really only you can make the right decision for you & your son, but since you asked "our" opinion, do you really want to spend your whole vacation pumping? Then to have your son off the breast for 17 days while you’re gone just to come home & try to reintroduce it just to wean at that point? I know for me the vacation would be a lot more enjoyable if I didn't have to worry about keeping up my supply & pumping the whole time. It sounds like if you were not taking this trip you would have weaned him at this time, so why not continue with your original plan?
So I know I’m not answering your question about stockpiling, but I did want to tell you not to worry so much, you have plenty of time, it's only February, if you decide to go with the weaning idea before your trip, you don't even have to worry about starting that process for 3 more months. Continue the joy of feeding your son for the next three months, then in April you can start the transition slow. I agree with the original posts about 1 feeding at a time for a week, then the next week remove two feeds a day for a week, ect…, my dr recommended that and it works well. If you feed 6 times a day then it may take 6 weeks. About a month before my daughters 1st b-day I gradually gave her a little cow’s milk ONLY in a sippy cup, just to get her used to the taste & the cup. By his 1st birthday he should be fine & you will be all set for your trip. Also, I know now at what 9 months old all these seems like a lot and he’s not ready, but the close he gets to his first birthday the easier it will be, he will be eating more table food, he will start drinking from a sippy cup more, he may even wean himself…
I was also just thinking from reading your question, if you don't want to ask your mother because she already thinks your off breast milk, how will she react to your bring over 17 days worth of milk while you’re gone?? Good luck and great job on breast feeding your son so long! Oh and I’m so jealous about your trip, have fun!