Baptism, Godparents, Party

Currently planning our daughters catholic baptism. We had chosen the godparents already and would like some input -

1. 3 of them are married so does that mean the spouse is a god parent?

2. We would like to take the godparents out after for lunch. Since we are keeping it small, do we invite the chosen godparents spouse?

3. How did you ask a godparent to be a godparent?

4. Any suggestions on where to buy a baptismal gown?

Any advice or suggestions we be helpful! Thank you!