Well, I certainly hope you plan to puchase him a park ticket, but that's a post for another topic...
Well really, I'm not sure what it is to you, but like I said, we have APs. So clearly he is taken care of. My point was that WDW doesn't need his correct age for our room for any reason as we are not sneaking in extra people (thereby needing him to be 2), we don't book packages (thereby not needing a ticket through it), and don't do the dining plan (so he's not missing out on the 'free' food during the time we'll be there). So just like they think he's 2yo now, I could just as well have said he is now 4yo and that would be that. They wouldn't have questioned it at all.
To get back on track, the rule is that a child must be 4, period. Not three and 11 months, not 3 and 9 months,
FOUR.
If you want to lie about it, for your own personal selfish reasons, no one can really stop you. Of course, THAT is also a post for another topic...
The OP asked if it was allowed, or if anyone had done it.
The answer is: it's NOT allowed. By Florida state law, it's NOT allowed. "You" (not you personally, but anyone who chooses to "sneak" their underage kid into the kid's club) want to break the law, go ahead. Be a GREAT example for your toddler...