Seamless? No. While an automatic transfer switch is designed to automatically switch over between shore and generator power, it is not designed to do it while under a heavy load, like air conditioning. If under load when switching, the contacts can arc, resulting in burned contacts that don't make a connection, or welded contacts that won't break a connection.
The auto transfer switch does make life easier. But the process is going to be pretty much what you describe: you will still want to turn off the A/C and other heavy loads before starting or stopping the generator and plugging or unplugging shore power.
If you don't have a transfer switch now, I'm guessing you have an outlet that is powered by the generator, and you plug your shore cord into that? Getting an automatic transfer switch will save you the effort of having to do that part.
I just bought this one: AirDream SofaBed Mattress
It replaces a virtually identical and rather comfortable mattress that came with the sofa bed, and finally after seven years was replaced because the air portion started leaking significantly (resisting my patch attempts) and the springs were starting to sag. Hopefully this one will perform as well as the old one (haven't slept on it yet.)