You do realize, of course, that the shelter is mainly for you so that you don't lie awake on nasty nights worrying about your babies. They never had man-made shelters on the moors. However, it is cheap and easy to make a shelter big enough for your little flock out of 2 cattle panels and a tarp. You tie the long sides together, overlapping sligtly. Then you use rope (binders twine?) to bow them so they are like a Quonset Hut from WWII. Cover with a tarp - hopefully it will be big enough to cover one end also - we are at about at 16' x 10' here, so you have either 1 16'x16' or a smaller one for the back and a 10'x16'. Peg it down with tent pegs making sure the back is to the prevailing wind. Even in snow, etc, you could rent out this little sucker if it had plumbing!
Toni