This is exactly the forum I was looking for! It's nice to know we aren't the only crazy ones out there!
We took our first trip with our oldest son at 12 months and went again with our second son when he was 10 months old. We were supposed to be leaving one month from now for our third sons first trip, but also were surprised with a fourth (and final) addition to the family. So, we are now planning to go when our new baby is either about three or five months old (end of November or end of January). We did have to postpone the trip, but already had park tickets, flights, etc. booked, so we do have to go relatively quickly after the baby is born.
So, all that to be said, we will be taking a very young baby here soon (along with three other boys aged 1,3,5). I know that we will have to go verrrrrrry slow, but I think that we will have a ton of fun!