Semi-formal, but the majority of the time you will likely be outside so choose wisely. Also, you do not need to wear a specific color, the wedding will be in a garden and flowers come in all colors, so wear what you'd like to, except white.
Unless the family name is on the invitation envelope such as "The Smith Family" and unless the child's name is including on the envelope, please leave your children with a sitter. The reception will be taking place outdoors at night and we would hate it if one of them were to wander off and get lost.
No.
Also no.