You don't have to decide instantly what to do with your surplus and old 401k, forever and ever, amen. I think you might have some decision paralysis? Like if you're not sure what to do right now, you don't do anything? (Like not setting up your 401k right away.) Most of the time there are intermediate steps you can take, or ways to dial back or change directions later.
I don't see that you have your current cash balances listed? Do you have any savings for emergencies? I know a lot of people here prefer to rely on a Roth IRA, investments, and credit cards in case of a sudden huge expense or change in income, but I personally would prefer to start out with a pile of cash. If you don't have any emergency savings I personally would not proceed to invest your entire surplus immediately because you could easily lose a huge chunk of it if the market takes a plunge. If you need an emergency fund of $20k and you have $50k in your brokerage account already, that's fine, but if you need $20k, only have $20k, and put it all in your brokerage account and 2008 happens again at the same time you get laid off, that would be very bad.
If you have no emergency fund I'd split your surplus between savings and paying down those loans, at least until you get enough cash on hand to cover a sudden big expense like a new roof, unexpected medical bills, or car replacement.
I can't judge regarding the cars because we have three too (but we're not looking to retire early), but you might consider whether you need them around, especially if your wife doesn't have a commute and doesn't go out many days. It might make sense to keep the Sonata and Ranger for commuting and carting stuff around in, respectively. Does the Mercedes maybe have sentimental value?