Add another empty nester couple that cruise DCL with no kids. We started cruising back when our son was young and now he is jealous that we go and he can't because he has to work. There are times you will notice ALOT of kids, so don't let anyone blow smoke about that. In the atrium before dinners, during character greetings, running in the hallways at night, and around the pool areas. However, Disney does a great job at having spaces for adults to escape to. Although I am always sad to leave the ship, I am glad to be about the only one relaxed while leaving. All those parents that have overindulged their wee ones all week, are now dealing with over tired, overindulged, crying kids. Don't miss that one bit!
I would suggest a 4 day as a minimum because the 3 day just won't give you enough time to enjoy all the ship has to offer.
Internet was fine on the Fantasy. I signed up for the 50mb of free at the start of the week and didn't use it all. I mostly did emails. We were in two "U.S" ports (St Thomas, and San Juan Puerto Rico) so my cell service worked in both. Check your plan though, we could use text in St Thomas, but not voice or data. San Juan we could use either with no extra charges. (Verizon)