I would do what you want to do...why not start him? So what if it takes four months or longer and you are still training when you go. You CAN use "Feel and Learn" type pull-ups when you go to the parks if you think they will help. This will not scar him for life or set him back in his training. You are in a different environment when you are Disney and your child may not focus or be willing to stop when he needs to go to the bathroom (and you may not always be near one). If he is wearing feel and learn type pull-ups, you can bill them as "special underpants just for Disneyworld". You can still remind him/ask him if he needs to go potty and take him as frequently as possible. The pull-ups are a good back up in case no bathrooms are nearby and/or he forgets.
My almost four year old at the time had been completely potty trained for just about a year when we went to Disney. Yet, she had three accidents while we were there because she was too caught up on the fun to notice and/or she would say she didn't need to go when we asked her because she didn't want to stop what she was doing (and, in some cases, was afraid of the flushing sensors).
My point- I would start to train, if he is ready, but take pull-ups as a back up....just in case.
My almost four year old at the time had been completely potty trained for just about a year when we went to Disney. Yet, she had three accidents while we were there because she was too caught up on the fun to notice and/or she would say she didn't need to go when we asked her because she didn't want to stop what she was doing (and, in some cases, was afraid of the flushing sensors).
My point- I would start to train, if he is ready, but take pull-ups as a back up....just in case.