So many people on this site always repeat the "Airstreams are designed for two people". Sorry, but that's nonsense. Just because it's not for you, doesn't mean it won't work for others. This mantra seems to get repeated even more when folks mention small kids. When I first started posting, people told me, we'd go crazy, and it's impossible. Well, THEY ARE WRONG.
That being said, in your time frame, I would avoid and highly recommend NOT restoring an older Airstream. Depending on your budget, I would look for a unit produced after the year 2002.
While restoring an older unit can lead to greater customization, you have to consider all the things that will need repairing and upgrading.
We chose and found a 2007 27ft front bedroom Airstream International Signature for under 30K. We had one small area where the floor needed a patch but other than that it was livable from the start.
We made a few upgrades, new batteries, new tires and solar panels. We reupholstered our cushions, put down new laminate flooring and remodeled our bedroom.
With the slightly newer unit, we could get started on the customizing.
We made the space fit our needs. One of the things I did was remodel the bedroom. I work on the road fulltime, and wanted a dedicated work area. We also wanted a little more space for the kids on those rainy days.
My wife and I are used to sleeping in a small bed, we cuddle and enjoy it. So we built an extra large twin/lounge and a standing desk.
It really changed the experience and feel of the bedroom area. The space on the floor, really makes it feel open.
I can still stand and work, and there is room for our oldest to play on the floor and sit in her bean bag chair. I often enjoy sitting in the bean bag chair to read on the floor, with my legs stretched out.
We added shelves to our wardrobe and other #Airganization items as we call it to suit our needs.
We even customized the fridge, it now has magnetic fronts, the lower half is a chalkboard for the kids and the top half a white board for mom and dad.
Everyone has different needs and a different lifestyle. To be honest, we just don't have that much crap. We're minimalist. There are single retirees on this site with more stuff than a family of 4. Be careful whose advice you take seriously. Look for folks who share a similar experience or are living close to how you want to live. Ask their advice and plan in a way that reflects your lifestyle, values, and needs.
It's important to think about how you will live, and start visualizing that. And thinking about what you actually need to live.
You will be surprised to discover you can do with a lot less, be happier and enjoy more time as a family.
So to conclude this, I would look for a unit that you could focus on customizing rather than completely remodeling/restoring. 3 months is unrealistic.
We purchased our Airstream in August 2014 and it took me a number of months to get it to where it is now. And I wasn't restoring it, and still working around a work schedule.
Good luck in your adventures. And if you want to pick my brain, you can find me faster on FB: https://www.facebook.com/boldadventure/