You are just awesome, Z! A surprise Disney Cruise vacation will definitely be on your wife's top list of awesome acts that you've done for your family. What a great plan you've got going. You definitely want to carve out time for you and your wife to spend a romantic evening together -- it's a must.
I would suggest that you coordinate the dinner schedule with a reservation at the
Nursery for your son. You can check him in there a few minutes before dinner time and even coordinate his dinner and evening routine with one of the youth counselors. You might also want to bring his sleeping clothes, so that the youth counselors can change him for bedtime. You can leave instructions with them and they'll take care of everything for you, so that you can enjoy a romantic evening.
They have a quiet room with cribs that he can sleep in while in there. Just in case you end up taking more time that night -- this always happens to us -- you can just make a quick phone call to the Nursery to let them know that you're running late. They usually close at 11pm (but check their hours each night, just in case something changes)... you should be able to get through dinner, and maybe hop on over to one of the night clubs for after dinner drinks and dancing.
Remember -- date night can be every night on a Disney Cruise!
Hope this helps, Z. Do let us know if you have any additional questions that we can help with.
Have a great day!
~Dolly