I agree about skipping the water parks in February, especially since your DD is so young. She'll enjoy the pool just as much if you're lucky enough for it to be warm enough (they usually heat them anyhow). I would let her enjoy the parks more. As for not getting a park hopper, I would check the park schedules first. Some parks, like AK, close at around 5 pm in the winter months, and if you have a hopper, you could still go back to another park in the evening to enjoy the fireworks or extra magic hours if your DD has a nap and is up for it. I especially like the hoppers in case there's something you miss doing at a park because little ones have a meltdown, get tired, or someone doesn't feel up to it, you can always go back the next day and just do that one thing and then move on to another park.
To sum up, skip the water parks in Feb. and go for the park hopper.
Have a wonderful, magical time!