You're going to have a great time!
We have a 25 and really, really like it. There are pros and cons to every size Airstream so don't doubt your decision. There is no perfect size/configuration for all that you will do. There are times I want a smaller trailer and times I want bigger. That's just life
! They are all wonderful!
Everyone has posted good info so all I can add is get equipment that you feel you need based on what folks have shared and don't sweat the rest until after you get out there for a close-by overnight experience. That will let you know what else you would like to make things more comfortable or safer. Have fun!