Try to get
Art Ludwig's book, "Creating an Oasis with Greywater," which will give you lots of advice and details.
Yes, greywater stored for two days will smell, but hopefully only annoy people who stick their noses right over the barrels.
I don't know about using it for the lawn. It might be kind of yucky on the lawn, and you'll probably want to sprinkle it in with fresh water after application.
I use small barrels of greywater that I store for a few days, but I pour them under plants, onto mulch or plain soil, where it soaks in quickly. It doesn't smell after 5 minutes, often even after 1 minute but surely after 5.