I think you should make things as easy on yourself as possible and yes if that means having picnic lunchs then do so. Why not stay in if you can so you don't have to put the kids in and out of the stroller. Have you seen a chiropractor? I see one for my feet and the relief is incredible.
Can anyone help you with the kids during meal and naptimes?
Sorry you are going through this, you must feel so miserable. I hope your shoulder is better soon.