Have rented from them locally, without any problem, but not MCO. They are the parent company of National & Alamo. They are now inside terminal so no shuttle needed. If you have a good rate, then I wouldn't hesitate to use them. Don't know if you have to go to counter or if you can go straight out to the garage and check in there.
I have rented from them at MCO and elsewhere. Always had good service. They can sometimes be higher in price, but the things I like is that they let you have input into what kind of car you get. My daughter uses a wheelchair and we're picky about rental cars since we need to be able to fit her chair in the back, and her in the front seat. Enterprise has been the best about letting us look at different models. Most places just assign you a random car. So, if you have a good rate, I think you'll be very happy.
If it goes to the garage where all the other rental companies are there are always guys with trolleys that will help you. Worth the $$ I usually pay a buck or 2 per bag!
Not sure what you mean by delivering! You return the car to the same garage you picked it up in. As far as luggage, are other people traveling with you? If you are dropping them off, let them take the luggage, then you drive around return car and walk to the terminal and meet up with them. If you have all that luggage just for yourself, you can only carry on one bag and small personal item, everything else will need to be checked. In that case I would go to terminal and use a skycap to check your bags then return the car.
Are you staying on Disney property? Use the RAC program to check your bags at the resort then you only have to worry about your carry ons.
We rented from Enterprise on our trip last month and we were very happy with them. They were easy to find, there was no line to check in when we got to the airport. When we went to the garage, they took out down the row of cars and pick out which one we wanted. Dropping the car back off was very easy as well. They were the lowest price we could find for our dates and we are happy that we went with them.