One year is not a big deal and I would not start the engine unless I were to drive it.
Setting with just an idle is not good for the valves they tend to carbon up.
The gen set does need to be run from time to time and always under a load.
Tires..90% of RV tires dry rot long before they wear out and being parked for a year is not a death certificate even parked on the grass.
IMHO Driving the RV for minimum 30 miles once every other month with the genset running is the best thing you can do for your RV and covering and uncovering is a major job.