Big enough for 3 Easter Eggers?

[aart]

It's a 4 ft fence, and if we have issues I think we'll be covering it with some poultry netting to keep them in. If that starts to happen, we'll probably have to change plans and add a run!

Adding some poultry netting might work until the snow flies....but even my 14ga 2x4 welded wire run roof, supported at 6' spans, grabs wet snow and starts to seriously sag.
Keep snow loads and clearing in mind with all your plans/mods.