Gosh they'd have a heck of a lot of fun climbing all over that thing lol! They'd even go down the slide if you left it on! As far as actual shelter, unless you add on it might be a bit small. If I'm correct in assuming that the large, center square area would be the enclosed shelter part...
A big X2 on that advice! No chicken feed. It wouldn't hurt to put them on good quality grass hay either and then maybe give some pelleted complete feed on the side to supplement since they are young. I really don't like giving grain to goats at all unless they are milking. Alfalfa also is...