First, this is not a question of separating money, but a which product to choose. So put away the torches and pitchforks.
So, in researching for my wife's sole proprietorship LLC, we can't find a shred of reason to use a business checking account from our bank versus a personal checking account. The only advantage I see is a business account has her business name on the checks, and we can have multiple designated signers...
Other than that, the cheapest business accounts limit us to 100 transactions per month and $2500 in cash deposits (Bank of the West). So if she collects cash for a service she would have to deposit it in a personal account and write a check to her business account (slippery slope in terms of cash intermingling.)
Your plain old checking account that you, your kids, and your grand mama have... Down side, invoices would have to say pay to the order of my wife... and that looks less professional- but it's legal.
So, any thoughts? Thanks everyone! And as a reminder, regardless of product this account is strictly used for the LLC- absolutely no personal use ever.