4:27pm flight departure will put you on a 1:30ish DME bus. Be at the bus stop, ready to go, at least 15 mins before the appointed time. That time is the time the bus leaves the resort, NOT the time you should arrive. Can't tell you how many times I've seen families running up to the bus just as it is closing the doors!!!
For a 10:30 ADR at CM's, try to get there a bit early. You may be able to get in a bit early. Then, you need to allow enough time to return to POP. It is always wise to allow an hour to get from resort to resort if using Disney transportation. If you get close to noontime, and are still at the restaurant, I would just take a cab back to POP. Much less stressful.