Take a cab. Buses are not guaranteed from TTC to Epcot (though sometimes you'll get lucky and one will take you there).
Those of you worried about getting to MK early, you'll be fine, as the boats will be running even if the monorail is down. Getting to Epcot for PPO ADRs is the biggest issue, and after several problems, we just cab it now. (This is my ONLY complaint about the Poly!!!!) There are always cabs sitting next to the Poly bus stop and it's about a $12 ride. Totally worth not sweating how to get there. And Florida law doesn't require boosters, so no need to worry about that.