I would have a hat/fascinator in my hair too, and take a shawl/pashmina to the wedding JIC you feel you want to cover your shoulders for part of it. I know when I'm in something strappy I can feel a little underdressed at times... but then again, you'll be in the height of summer so it will be less of an issue. I'm in the land of permanent cold and am ALWAYS half-frozen.

and I'm sure your children ALWAYS have nice things to wear... but they may need something different for the wedding.