For trail and desert 31" tires would probably be more then serviceable, and a lot easier to fit and power then 34" tires. And they will also fit fine with just a standard SPOA, 34" tires are going to require a SPOA + some heavy fender trimming or additional lift from YJ springs or an alternative path.
With the flat towing being used I would avoid a spool in the rear. It will cause drag on your tires and unnecessary stress on your rear axles.
I would go with a SPOA and 31" tires first. Probably a high steer kit in the front and a traction bar in the back to avoid axle wrap, since you are planning on playing in the sand. See how you like it, then go for a transfer case, lockers, skid plates, axles, and whatever from there.