choose between not perfect applicant and future perfect one

[Ping W.]

I have a couple with 6 kids ranging from age 20 to age 4 applied our house. They told me their credit is not so good but they are working on it so that they could buy a house of their own one day. The previous landlord told me good stuff about them. They have to move out because the house was sold and they would move in as soon as I approve them. I was thinking of approving them but hesitating on their not so good credit history and big family of 8.

To add to that a potential perfect tenant just contacted me. He is retired military and works for the government now. Only tenant would be husband and wife.  No pet.  Credit: 700+ but they would move in mid Dec. The earliest they could see our house is Sat. and they would see houses whole day Sat. I am very confident they would like our house but I don't know for sure until they apply for it. I definitely prefer them over the other big family but I am afraid I would loose the other family if I wait another 2-3 day for their decision because the first family is looking to move in right away.

We would you choose?