STD evelope wording

I feel so clueless about this, a few questions:
If we are inviting someone with a guest do we include the guests name on the STD envelople.
Also a family with children how do we write that on the STD envelople?

For the people who we are inviting with a guest that is to be determined, we didn't include and guest on the envelope. For people who were bringing a guest that is known to us, we included their name on the envelope underneath the main person we were inviting.

For families with children, we addressed to Mr and Mrs X and family.

For those with Significant Others, we included them on the STD envelope. If we are planning to invite someone with a guest who is unknown to us, we addressed the STD to only the family member or friend.

For those with children: If you are planning to invite the children to the wedding, address the STD to Mr. & Mrs. Smith and Family. If you are not planning to invite the kids to the wedding, just address it to Mr. & Mrs. Smith.

HTH