We just got off the Magic and yes they still offer the Evian water bottle package. I honestly don't recall the price but it is VERY expensive. We purchased a case before the cruise and put it in a box (for baby's formula) and put a luggage tag on it and had no problems getting it on. I wrapped the bottled water cases in a garbage bag just in case.
Last year's cruise, we were without baby and just had DD4 and put the water in our suitcase.
Just a heads up, if you are wanting to take any of the leftover bottles off with you in the box, bring your own packing tape. I brought my own packing tape but ran out and it was quite difficult to get guest services to part with their only roll. I had to talk to 4 guest services personnel before I got one that actually didn't "pretend" they didn't have any.