One thing I forgot to mention is that you will need a clutch mechanism to disengage the tracking drive while slewing in azimuth and to re-engage it at the end of the slew, but first, detach the azimuth slew. This can be fairly easily accomplished with a single push-button switch that, when pressed, closes the circuit that magnetically disengages the tracking clutch and, a few milliseconds later, engages the slew stepper. Similarly, when the button is released, the slew motor stops first, and then the clutch, under spring tension, closes. Somewhere in that description, you need to add the idea of engaging and disengaging the slew motor, possibly with another magnetic clutch.
Be prepared to bring a substantial amount of battery power. I would recommend Lithium as it can be safely discharged to 5 or 10%, whereas Lead Acid is best at 20% discharge, but is commonly discharged at 50%. Additionally, Lithium weighs 30lbs, whereas Lead weighs almost 70lbs.