Hi there Reya, and welcome to the Disney Parks Moms Panel from a fellow Floridian!
For my family, Disney's Florida Resident Seasonal Pass program has been the perfect fit. We can take advantage of living close to the Walt Disney World Resort and visit almost any time we like, at a lower cost than the Florida Resident Annual Pass. But I'll be honest, when those blockout times hit, I start thinking about an upgrade too!
As long as your Seasonal Pass hasn't expired, you can upgrade to the Florida Resident Annual Pass. You should be able to just pay the difference between your Seasonal Pass and the amount of the new pass. The expiration date will likely depend on how long you've had your current pass. If you're coming up on the renewal period (about 30 days before your pass expires), it will be good for another year. If you've only had the current pass for a few months, the expiration date on your new Annual Pass will be the same as your current Seasonal one.
Your best bet is to call Guest Services and speak to a Cast Member about what you'd like to do and find out exactly what your particular options are, including how much your new pass will cost.
I hope this helps you and your family enjoy lots of Disney days to come, Reya. Have a magical day!
Kathy K.