We have to use every drop of water sparingly, thus we use all household used water for the garden. Water is metered, like many parts of the UK so it can become very expensive blanket watering. I have tried to plant the vegetables using taller plants to shade the smaller ones, does not make for a very tidy, straight row garden. But the Sweetcorn shelter the runner beans who shelter the marrows and melons and peas, they grow up sticks, unlike the Bulgarian way my neighbour uses, these in turn provide shade for cabbage. The peppers, provide shade for Brocolli.
The parsnips grow in pots under shade by the shed.
As for the enquery regarding watering while away, a friend or neighbour is your best bet, you can do theirs when they go away.