"Hard" is kind of subjective. The smallest table in the MDRs seats 4, so you would be at a table with three empty seats. I believe Disney would accommodate you if they could...depends on the context of how full the cruise is, and how many other requests (especially couples) there are for private tables. It never hurts to ask! Just call
DCL and give them that request; if it's important, and you find out when you board that you didn't get a single table, you could ask again at the table change location.
Good luck!
p.s. To add to my answer, if I may be allowed a personal opinion (even though you didn't ask), if you can't have your own table I bet you'll enjoy spending dinners a cruise with other folks who also similarly Disney lovers