You don't need your birth certificate, because your passport is your proof of ID.
You DO need your childrens' birth certificates though, to prove how they are related to you, along with their passports and the letters showing their address.
For the documents addressed to you and your husband, you just need 6 with each name on, so they can be a mixture of joint and separate.
So, you could use:
- 3 joint documents addressed to both of you
- 6 separately addressed documents (3 in each name)
Can you post the dates and type of each of the documents addressed to you, just to check that they meet the requirements?