I would be careful of a trickle charger. Maybe a good float charger instead. Or if you are around just hook trickle charger up once a month.
A few years is going to be a long time for a tank of today's gas; can you find non ethanol gas near you? Google ethanol-free gas. It lasts longer.
Starting it without bringing it up to temp can cause moisture problems in the engine. You might change the oil after a year of two.
Insurance might be a problem but if you get a chance take it out for a good run when you can.