We’ve played with a lot of different technologies at the farmer’s market. Electronics used outdoors need to be rugged, easy to protect from rain, and usable in bright sunshine.
Back when we made people order fryers in advance, we brought a Panasonic ToughBook so we could take the deposits and enter the orders on QuickBooks. We stopped doing this when we started bringing chickens on spec, rather than just to fill orders. Because every cop car in the country seems to be equipped with one of these, used ToughBooks are plentiful and affordable on eBay and other places.