HI Jacqueline!
You just described the nEARly perfect Walt Disney World vacation!
Now, a vacation in Walt Disney World may not be "cheap", but it is always a tremendous VALUE. If you plan to stay at a Walt Disney World Resort, you not only have the opportunity to choose from a variety of Value Resorts, but also Value Seasons. Value Season is now divided into Value 1 and Value 2 Season, with slightly different pricing for each. If you would like to see some of the offerings in this category, click on this link,
here, to get started.
As for shortest lines, I have found, based upon my personal experience, that certain months have lower crowd levels. We enjoy going during January, February, September, and November. Crowd levels tend to pick up during the holidays, special events (such as races, EPCOT's International Food & Wine Festival, and also during the months of spring and summer breaks for the schools.
As for weather, Florida can get REALLY hot during the summer, so that is probably not the best time for you! Again, we love it during November, January and February, for the weather AND the low crowd levels most days. However, please be advised that special events (and holidays) are scheduled during these months, so you will need to check the calendar for those, which could affect crowd levels. And a heat wave can happen in Florida at any time of the year! Thankfully, even if you visit during the hottest months, there are so many air conditioned attractions throughout the parks that you'll find plenty of opportunities to cool off.
I hope your vacation turns out to be the perfect balance of Disney Magic for you. But, you know, the PERFECT Disney Vacation is ANY Disney Vacation! Have a magical time!