If light winds are forecast then I reckon those big fat knobblies should almost just about do it. maybe 3-4 spares JUST IN CASE
I find that the my club 88 (ribbed tyres) only needs new shoes when the wind is blowing and that is on limestone (lake Walyungup), maybe every 3-4 weeks. The knobblies are heavier and harder to get going than ribbed tyres but they do last a lot longer I still have a set attached to the original rims I turfed to the garage from when I first started sailing my LLM, they lasted a full season (no racing).
Also the psi of the tyre and the rolling resistance of your bearings will play a big part too. The fella who won the mini/blokarting races at Lefroy last year had his rear tyres inflated to 45psi (I'm not endorsing this) and used wet towels in between races to ensure they didn't pop in the heat. If your bearings still have the packing grease in them, soak them in petrol to dissolve the grease and lube them with a light oil or some fellas use inox. I also remove the bearing seal facing the inside of the wheel to further reduce resistance.
Probably just common sense but if you can, latch onto a more experienced sailor and follow them as they will inadvertently help you find the best places to tack and where to point too, not that it helps me much

I still manage to muck things up at some stage
good luck mate not coming last in every race is a buzz in itself