Look at the brady installation pdf I pointed at before. If your soil isn't rocky enough to bother it, the process is really simple, and the points are $10 - $20 each. You wouldn't have to put them right next to the house, and you could combine that water with the sump water if needed.
An unwanted cheap backyard swimming pool can make a usable tank if you choose to go that way. An old spa probably would hold 250 or so gallons.
But it would probably be cheapest to just segmant your sprinkler system into smaller zones, and use the sump water.