-Don't change anything too close to travel. For example, don't take the passy or the bottle away within a month or so before you leave. Don't start potty training or switching to a toddle bed. All of these things stress a kid and you want them at their best for travel.
-Try to keep things to normal as possible. If your child sleeps in a full size crib at home, consider renting one for the trip. If you have a pack and play at home, and want them to sleep in one at WDW, have a trial run at home to see how they do. Consider taking their own sheets so they will smell like home.
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forget green for a few days.....Make things easy. Take disposable sippy cups ( we would rewash for times other than milk in the parks, but they are cheap and no big deal if you loose a few)disposable changing pads, bibs, place mats etc. Be sure to try the sippy cups at home first to be sure that you child is ok with them. (also been there done that one)
-Take extra clothes and PJs if you don't want to wash. Babies clothes are tiny nd take little room. Accidents happen. Dress for comfort rather than cute. Much happier baby.
-Pack everything you could need, Bath products (don't want to risk a new brand), any medications (with a doctors ok to give them),pedialite (been there ..done that one).
-Have a good stroller, consider a wrap /carrier if you think standing in line may be an issue, and consider a lease if you think that would work for your family and make your child and you happier.
-Know your child.....will you be able to keep him out late and he sleep in the stroller or be happy, or do you have a kid that really needs to stay on his routine. Plan accordingly. I had one of each
-Remember that babies can go on anything without a height restriction and that is a LOT! Most times at 19 mo, the only fears are dark or loud noises....not content. HM would not likely scare him unless he is afraid of the dark.
-Plan well for TS meals. Try to plan when she is hungry but not starving and choose places where there is lots to see. Mine loved buffets at that age and I liked not having to wait for food. Have a few, new, quite toys for longer TS meals. I am was not above handing a toddler my iphone for a bit to allow us to finish dessert in peace

RFC sacred mine when they were little.
-Don't introduce any new foods during travel. Been there....done that one too. You never know what food a kid can react to.
-Carry a few toddler friendly food that you know she will like. Gerber Graduates are great, and feed he mostly off your plate if she will eat what you eat. Avoid lots of junk foods, not fun for an upset tummy on vacation.
-Remember that it's your vacation too! She willl love just being with you. Strolling around WS with you and spaceship earth will impress her as much as pooh!
-ENJOY......its such a fun age!!!