Of course. Children are more than welcome to join the party.
Yes - please just try to limit it to just one.
Dressy casual. Keep it nice and comfortable. No need to come wearing a suit or fancy dress.
The celebration is more "open house" style. Stop by any time between 5:30-8:30pm. We'd love to see you, but completely understand if you can't make it.
Then you better bring a lawn chair and a sandwich. :)