Yes, it is entirely possible, BUT... just remember that the Magical Express bus typically will pick you up at the hotel about 3 hours before your flight departure time, so in your case the bus will come at around 12:30pm. And keep in mind that you need to catch a bus from the MK back to your hotel. However long you think this may take, double that amount of time to account for unexpected delays. Last year when we did this, just as our bus from MGM was pulling into the hotel parking lot, we saw the ME bus pulling away. At MGM we just missed one bus then had to wait 20 minutes for the next one; meanwhile at our hotel, the ME bus arrived & left a few minutes early.
So if you are willing to leave MK by 11am and use a day's worth of admission for just a few hours in the morning, I say go for it and have a great time!! It sure beats sitting around the hotel being sad because you are just waiting to go home.
And yes, the resorts have 'luggage services' where they will hold your luggage while you are out & about, whether you are using ME or not. Keep in mind you will also need some time to claim your bags upon your return to the resort.