Where are you planning on staying?
this is my #1 question when people say they are traveling with young kids. Given you will be taking trips back and forth to the resort for breaks and naps, travel time AND travel mode are important considerations.
If your wife is like mine with babies, I could have rented a U-Haul to pull around the park—extra diapers, food, changes of clothing, etc. Strollers are great pack mules when in the park, but be advised that you have to fold them up whenever you get on a WDW bus—which means that anything that went in there, must come out. And guess who gets to hold it all? you!
However, if you are staying anywhere with either monorail or friendship boat transportation, you do not need to fold those rolling cargo carriers up. Huge time, hassle, frustration and back saver.
That aside, be sure to plan lots of character interactions like character meals—you have to eat and kids are generally happier when they a munching on something. Plan FPs for other Character interactions b/c any attraction that would be suitable for an 18mo old generally doesn't have huge lines (Except Peter Pan lol). Then take advantage of rider swap and single rider lines for the adults to have some fun too!!!
You can even game the system a bit and double up on your FP's by making individual FP's for different attractions and using rider swap—Say you make a FP for Space Mnt, and your wife makes one for BTM, you use your FP while the wife watches the kid, then do a rider swap where she gets to go on SM though the FP line. Then when you go to use her BTM, she goes first while you watch the kid and then you claim the rider swap.
Know the location of the baby stations. They have anything you need for purchase in case you forgot anything (baby wipes, ointments, etc) and its a good place to get away from the crowds for feedings, a little rest, etc.
Resorts rent cribs so you don't need to lug your pack and play if you don't want. Flying? If you have a seat for the child, we always choose to bring the car seat with us. Yes, its a pain to lug, but it does not count as a "bag" and the baby feels more 'at home' in the car seat then on the regular, stiff airline seat. Also, try and plan your flight during nap or sleep times as often they will naturally fall asleep b/c their bodies are conditioned to it.
Likewise, don't try and squeeze those last few hours in the park on you last day and get the latest flight out, everyone just ends up hot, cranky and the ride home sucks. We normally just plan on checking out, grabbing breakfast and saying "see ya next time"
otherwise, just go with the baby's flow and enjoy the memories....Take lots of pictures!!!!