we just took our 14 month old - she's not always an easy baby at home, but it wasn't too bad on holiday.
things that helped.....
we shared our holiday with 2 other familys - not all day every day, but we did see them most days. That meant that we could occasionally go on a ride together and there was someone to watch the baby - it was an essential but it made life easier.
we took a longer trp - 14 nights - so we could take things slowly and have busy days and quieter days.
At home my dd is extremely stubborn, will not be fed by anyone (she likes to feed herself), needs a 3 hour nap in her own cot most days, frequently wakes in the night, had just learned to walk, and has developed an unhealthy obsession for pens and screams when you try and take them off her.
While we were away, she was basically the same - still stubborn, still didn't want to be fed, improved her walking immensly, and there weren't many pens so that was less of an issue.
She did manage to nap in the stroller which was something I had worried about - we decided we would go back to the room if necessary but it never became an issue. Only one evening did she get really fussy and I ended up taking her to the babycare center and giving her a bottle in the nursing room where it was dark and quiet, and she settled down after that - the rest of the time she would just fuss a little, and I would lie her stroller flat and pull the hood right down so it was sort of private and she would fall asleep.
I was worried about her waking in the night, but I think because we were so busy during the day, she was just tired, she never woke once, and touch wood she hasn't woken since we got home.
I didn't drive there, but we have a 9 hour flight and I have to tell you I was dreading it. We didn't have a seat booked for her, so I was expecting to have her on my knee for the journey, but fortunately the flight was empty so she got her own seat (but we didn't have a carseat for her). She was really good, she sat and looked at her books, and I played some games with her and sang some songs (very quietly), we took a little walk around the plane and then she fell asleep for her usual 4 hour nap which wasa big relief.
The one thing that was a struggle was food. She doesn't really eat baby food anymore, she mostly eats finger foods - she won't be fed, so we give her pieces of our dinner which are easy for her to eat herself. This isn't really a problem at home, but the food you eat on holiday isn't the greatest food for a baby. My dd ate far more fries and bits of chicken strips or hamburgers than I was comfortable with. We did have some fancier meals like buffets where she had rice or pasta and veggies, and she was obvisously quite pleased to have them, so she missed the nicer food too. I tried to take some babyfood for her to eat to balance her diet a little, but she was not prepared to be fed, and the mess if I gave her babyfood to feed herself is unreal. We did carry some yoghurt type things that didn't need refridgeration and she sometimes had that if she held one spoon and I had another. I would have to say food was our biggest battleground.
One word on babyfood - you are allowed to bring babyfood in glass jars into the parks, but be careful - I had some in my backpack and when I opened the the backpack at the security check the jar lept out of my bag and smashed everywhere - I was mortified. Security were very good and closed the area and got it cleaned up, but I didn't carry glass jars after that.
To allow my dd a little bit of freedom and exercise, we used a safety harness (leash) and whenever we stopped for a rest I would take her out of the stroller and we would let her walk around on the harness.
I have also taken a 3 year old to Disney, and while the issues are different I would say it is EASIER to take the baby, but the 3 year old will get more out of the experience (however, she is also more likely to be scared) the baby was scared of characters but didn't mind any ride, where as my dd1 at age 3 was terrified on most dark rides.
