A three sided shelter will work just fine in warmer weather - as they'll choose to lay right out in the rain or inclement weather even if they have a fancy barn!
As for feeding - they'd prefer to graze on your grass if that's possible, but if not possible, I buy Purina Duck Grower to feed to all of my waterfowl - and my geese love it!
So...they are pretty low maintenance, right? Where do they lay their eggs and how do you find them if they are free range all the time???
Or do you just not worry about or collect Goose eggs???
Well, if you provide them with a fairly large dog box, or a 3 sided shelter, etc., they should lay in the box or shelter you've provided.
Even free ranging - my geese always have gone back to their "house" to lay their eggs. I usually keep them contained in an enclosure attached to their house until they know their house. That kind of ensures that they go back there to lay when free ranging.
And of course I worry about getting those goose eggs! We eat whatever we're not selling, hatching, or the geese aren't setting on.