Congrats on your opportunity!
My two cents:
Pay off cc's, then cut them up but don't cancel them
Use $320 per month to pay down student loan.
Then think about what you want.
I note that with a wife at home, you are still paying $800 per month for food, and $140 for household/target. Even though total income is $3400 unreliable per month. This explains why your cc's are creeping up on you. Your saving grace is relatively low rent, which says that you don't demand fancy per se as a lifestyle choice.
I would not start a business until you can get your personal finances in order, else business and personal finances will get confused, kid situations can be difficult around a business, etc. Likewise don't touch it except to pay off existing debts or it will inflate your lifestyle and be gone before you can make best use of it.
This money is your means to start over.. If you don't think your job pay and security will increase rapidly in next few years, then you need to seriously consider moving to a lower cost town in California, or better yet out of state.
You could likely find an equally good job, and maybe that ice cream truck ( summer only stand) for you wife to manage in a small summer resort town, for example. Many small towns would have that $50 k down payment and leave a very small MTG... Ideal situation for launching a business. You can always plan to retire (early back to where you are now in 12 years with kids in college).
If not a big change first,, then one of two things will happen- you will start eating through that fund in less than 5years, or your wife will be stuck in a full time job that she does not like, for the money. Hopefully she will like it though... But chances are she will always want that business and never get it.
If this is too negative, it is not meant to be.. I have moved twice out of state, and moving is not a horrible thing you can't undo, sometimes it is a bit worse that current, but often it can be much better!
Good luck!