Invitation and consulate letters, which one is advised?

[mrnnmr]

I have my parents interview next week. My husband is sponsoring their visa, although we both are working.

I had initially sent them (mailed to my parents)a Letter to consulate (from sponsor), where in the letter was from my husband and no where it had mentioned my name and also only my husband who is the sponsor has signed the letter of consulate

I had also mailed the invitation letter which was again From my husband stating his name and no where in the document it was worded that both of us are inviting my parents, it only worded like my husband is inviting his in-laws and also had only my husband's signature on it.

I read in some forums that its better that both me and my husband word that we are both inviting them in the invitation letter and both of us sign. There fore i mailed again with another copies to my parents with letter to consulate where in both of us have signed, and the invitation letter from my husband , but worded that both of us are inviting them and both have signed the letter.

So now i need to decide as to which one should my parents carry for the interview amongst the below

1) Letter to consulate from my husband(sponsor) wording only his name and signed only by him

OR

Letter to consulate from my husband(sponsor) wording ONLY his name but signed by BOTH of us

2)Invitation letter from my husband(sponsor) wording ONLY his name that he is inviting his in-laws and signed ONLY by him

OR
Invitation letter from my husband(sponsor) wording BOTH our name that we are inviting my parents and signed by BOTH of us

Please advice.

Thanks