Kerrie,
I am a bit biased, so I would say 7 days over 5. But of course you can have a great Walt Disney World vacation in just 5 days too!
With a first vacation, and a 7 year old girl, I would do this;
- 3 days at the Magic Kingdom
- 1 day each at Hollywood Studios, Epcot, and Animal Kingdom
- 1 day assumed to be too busy traveling to or from Orlando, with no park that day
On your arrival day I would plan no park time, opting instead for some resort relaxation and exploration. Also, plan a great, fun, entertaining meal to kick off your trip in the right spirit.
While the Park Hopper option is great, on a first trip you have so much to discover at each park that you can forgo this cost.
That should get your planning started. Let's chat about extras after you get your exact travel dates, and you let me know a bit about what you are looking for in the realm of "extras".
Have a magical vacation!