Hello Angela, thanks for bringing your question to the Disney Parks Moms Panel. There are so many opinions on this question, and I'm sure that if a different panelist had answered it it would be completely different from my response. Everyone has their own idea of what a perfect length of stay is, and really it just depends.
There are a couple of things to consider before you plan on length. First thing is your budget. If your budget is going to limit the length of your stay, I would first figure out how to maximize the days spent in the parks. Meaning, if I had to move from a Moderate resort hotel to a Value resort hotel just so that I could extend my stay, I would. Secondly, are you on a time constraint? People have jobs and other responsibilities that demand their presence, so it might determine how much time you can stay.
Those realities aside, I would suggest a park a day, and Magic Kingdom twice. That would make a 5 night trip. There is so much to see and do at Walt Disney World, and I think that a 5 night vacation would be a good length for your family's first vacation. This way, you can go to each park and create your own experiences and use them for future reference. If you find out that one day is simply not enough to spend in Animal Kingdom, you will know that and use it when you go to plan another trip. We always end up spending the most time at The Magic Kingdom, which is why I suggest planning two days at this park. The Magic Kingdom also has lots of slow attractions like
it's a small world that your 1-year-old will love.
If you have any more questions please don't hesitate to ask. Happy planning, and have a magical first family vacation to Walt Disney World.