We used Magical Express last time we flew out of Calgary.
As others have mentioned, you pre-clear US Customs, so it is your choice as to whether you want ME to handle your luggage in Orlando. If you do not want to pick up your luggage in Orlando, make sure the tags are attached when you send the bags down the belt. If you would like to pick up your bags and take them with you to the ME counter, do not put ME tags on them. Pick them up and then take them with you to ME counter and they will ensure they go on the bus with you.
Which method you should choose may depend on your arrival time. We let ME handle our bags for a flight arriving in the evening, and had a long wait for the bags when we would have rather been sleeping. If you are arriving earlier in the day and then going to a park, or will have to wait to get your room anyway, then it can be easier to have ME take care of your luggage. In either case, make sure you have any absolute essentials (prescriptions, ID, money/wallet) in your carry-on. You never know when a bag will be lost.