We did this when my kids when we needed to escape from NY that had been hit with multiple snow storms. It was also last minute. I had DVC points so that part for us was inexpensive. Not having to rent a car is also a big saver at a peak time. The problem we ran into is that even in Florida, the alternatives to Disney are not as child friendly as far as entertainment and the ocean and gulf waters are cool in Feb. unless you head much further south. I totally get that it is easy to do this trip and can tell you it worked well for us.
There is a bit of temptation when you are there bc everyone is talking about going to this park and that. So be prepared for that. I would stay away from character meals bc, imho, it just adds to that temptation. We stayed at SSR and I would definitely stay at Port Orleans. It is much less in your face Disney compared to Art of Animation. And yes, the boat ride to Disney Springs and the
Lego store can be fun for kids. My kids (even though they are now teens) work as a team and build and race cars everytime we go. It was awesome that trip to not be under any pressure to go anywhere at any time. I would look at Rainforest Café if on a budget--kids will enjoy and you can sign up for Landrys (spelling?) and get a discount. Also, you do not need a reservation-- you just get the next available table when you go. Compared to Disney food prices, it will be cheap! I have heard there is a great new pizza place in DTD that is counter service.
Make sure you are by the pools for the afternoon, the DJ dance party and games takes place and that will keep everyone happy. The hot air tethered balloon ride at Disney Springs is pretty reasonable if you go really early, I think. Lots of concerts, dance and hula hoop parties in the evening that will not cost you anything additional. Obvioulsy there is Splitsville, DQ and movies== but all could add $$.
We rented surrey bikes at the hotel which I think (but am not sure) you may be able to do at Port Orleans. Otherwise, we just enjoyed the pools and the resort amenities. I read a book and the kids were 100% entertained. Considering the alternative was to stay in the ice cold weather, they had no problem with not going to the parks.
SSR and Old Key West both have them and community halls which provide craft activities, games and usually air hockey or something. But OKW main pool is closed in Feb, I think. If you could afford it, you also may want to consider Kidani or Jambo House at AK. Two main feature pools, Kidani has community hall and tons of Animal stuff to do. Night vision goggles, campfire, drumming, painting of animals and all those great places to watch animals day and night. You can take that bus to Disney Springs, but are a little removed from all the hustle and bustle of people going to the parks.
I say go for it! I also had moments of, "is this crazy?". But I am so glad we did that trip!