We do it all the time. If I can't get a night at the end (or beginning) of my trip I just book into a value resort for the night. If you go to luggage services at your first resort, they will transfer all your luggage to your value (or wherever you book on Disney property) and you can go to the parks or whatever you like. Check in online and/or just stop by the front desk at the value resort when you're ready to go to your room (after 4pm). You can set Magic Express to drop you at one resort at the beginning and pick up from a different resort when you're ready to go back to the airport. Disney makes it all very easy.