They are leaner than chickens but it's still kind of the same concept- the breast should not be "bony". There should be at least a fair amount of meat on the breast, just more streamlined. If you're feeling the keel on the sides, that's bad..
Hopefully they're just either sore or don't have much muscle tone, yet.
They can be let loose, the same advice applies to any other peafowl- keep them confined for as long as possible before letting them out the first time etc. A run will be excellent, gives them a very clear view of their new home plus let the birds have room to run, flap.
Another idea, give several perches at varying heights to encourage them to hop up occasionally and roost off ground at night. Once they are in habit of roosting off night, remove most of the really low perches to force them to fly up a longer distance instead of "ladder hopping".