50/50 Pilsner extract to wheat extract or a blonde ale recipe would work.
Use a clean ale yeast like US-05 or liquid Chico yeast like WLP001.
Cascade, Lemon drop, Citra hops ... but go easy on the hopping because shandy beers are low IBU and light on alcohol.
Five gallons is typically enough for one can of liquid extract apiece - one Pils and one wheat. If you like dry extract, about 3lb each.