Grass needs very regular watering to establish - even at this time of year both seeds or turf need to stay damp so I would be waiting until you are there to establish that. In the meantime I'd be working on weed removal

Bore water can still give you a lovely garden - almost every house near us has a bore for the garden. Just be aware because of the minerals in it, the water can discoulour fences, bricks etc.

I think you could get some plants in. If you got them in soon, they would be fairly established before the heat of summer hit them. You can get really small ones for no much cost that tend to establish themselves faster.