Welcome, Marina!
Walt Disney World has recently updated mask requirements. The current rules for face-coverings state that for vaccinated guests, masks are optional at all indoor and outdoor locations. Masks are still required on all enclosed
Disney World transportation, which includes buses, monorails, and the
Disney Skyliner. I encourage you to keep an eye on the
Know Before You Go Page of the Walt Disney World website to keep up to date with the latest changes.
Guests who are not fully vaccinated and are ages 2 and older will be required to wear masks at all indoor locations, including restaurants, theme park attractions and queues, and all enclosed transportation. Since currently, vaccines are only available for children over the age of five, it sounds like your little guy falls into this group, unless he turns five before you go and can get vaccinated.
There are no exceptions made to the mask policy at this time, Marina, even with a doctor's note, so we've got to figure out a way to make masks a little more appealing to him for the minimal amount of time he'll need one. I find what works with my grandson, who is three, is to find masks with characters that he loves, like Spidermans. We have practiced with him at home with rewards - like an M&M for every five minutes he keeps the mask on or a little extra screen time. We've finally reached a point where both he and his two-year-old sister will mask up for short periods of time.
I wish you good luck, Marina! I know it's frustrating, but we can get through this!
Anna