I do think some afternoon shade would help on hot days but the wilting of your vegetables in the afternoon is more likely due to some type of root damage from a mole or vole or the obvious cause is dry soil. If you water well and use a mulch on top of the soil to keep it cool then poke around the rootzone for runways or a nearby entry hole. Most sun loving vegetables will recover and still produce once new roots are grown and the weather cools. Keep growing, Marianne Binetti