Hi Courtney,
I have both good news and bad news to share. First, the bad news: when purchasing the Disney Dining Plan, one of the requirements is that it needs to be purchased for every guest in your party. That would mean that you would need to purchase it for your 3 year old.
However, the good news is that in past years Walt Disney World has offered free dining in the fall. If that repeats itself this year, you may have the possibility of taking advantage of that. With this
special offer, you won't need to pay for the Disney Dining Plan for anyone!
Keep checking the special offers link in the previous paragraph as well as the
Disney Parks Blog to follow the release of special offers.
Thank you for your question; please let us know if we can help again.