Go to the Washington Post web site and search Carolyn Hax's advice columns. About a week or three ago she had a letter about just this situation, where a couple jaunted off for two weeks abroad and left a baby with grandma, who couldn't hack the 24/7 responsibility and work and waking, and grandma -- without asking the parents -- handed the baby off to sister, who then handed the baby off to an unrelated adult the sister knew but who was not the parents' friend or relative! Hax, who is very smart and savvy, basically said the parents had abdicated their parental responsibility by being gone so long and so far. Of course few cases would end up like this one, where a baby ended up in the care of someone who was a stranger to the parents after both MIL and sister couldn't handle the responsibility and 24/7 work, but it's an interesting read.
Personally, I would not leave my child with someone else for that length of time for any trip. A two-week European trip would be terrific for kids from about five up -- so wait until they are old enough and take them with you. I say that from experience because we go to England for two to four weeks a year to see our family there and it's been wonderful for our daughter who is now 10. As for adults who say "We just MUST get away," that's a lovely grown-up fantasy that should last a few days at most. It's too much to ask of other adults to take on your kids for two weeks while you're so far away you cannot reach home easily.
I just now read the "what happened" addition you made. Your husband's being so adamant about things means you are smart to talk about it now, but be sure he is clear on the fact (if this is indeed the fact) that this is a non-negotiable item. It's easy to say "He'll mellow once we have kids, he'll be more flexible," but people don't change their fundamental personalities once they have children; it's possible that kids will bring out the rigidity even more, especially if he was raised believing only method X is right for child-rearing and now that he has a child, doing X is the only way to go. If he's super-inflexible on some things now, he may be just as rigid or more so with kids. Think about whether you and he should take some parenting classes together now, before you're even pregnant, to be certain you are on the same page about discipline and schooling and friends -- not just travel. Having a third party like a counselor or class instructor talking to you both may show him that his way is not the only way, especially once kids are in the picture. Just a thought for you.