I understand why you don't welcome the responsibility. The "point person" for the publisher will need to handle all financial transactions (to keep the IRS happy). You absolutely need a co-author agreement, along with some financial things. At a minimum, you'll need to:
1. Receive the money into a bank account you must register with KDP
2. Put the money belonging to each author into separate accounts that don't co-mingle with the point person's own funds (I'd recommend having everyone set up a PayPal account.)
3. Deliver the royalty statement (along with any other correspondence) to each author by email or mail as soon as you get it.
4. Deliver a 1099 (if you're in the US) to each author at the end of the year that will take away part of the income the publisher will be telling the IRS that YOU have earned over the year. If it's not much, no big deal, but if the book is a success, you could get dinged for taxes on income you didn't get.
5. Whether or not you'll need a: franchise tax number, Employer identification number or trade name will depend on your state requirements. Also, whether or not you must withhold state tax or other taxes/assessments before giving the money to the other authors (and thereafter remitting to the state) also depends on your state.
The co-author agreement should also deal with: 1) Who retains custody of the original written manuscripts, notes, author copies (if any) and letters; 2) Notify everyone when a special event or deal is announced so you can decide whether to participate; and 3) Who pays the bills out of their pocket for reimbursement? For example, the publisher might have as a clause (you mentioned Kindle, and they do) that in the event someone returns a copy or demands their money back, the publisher will, in turn, demand ITS money back--from the author. That little tidbit is here (emphasis mine):
5.4.7 Offsets, etc. We can withhold Royalties and offset them against future payments as indicated below. Our exercise of these rights does not limit other rights we may have to withhold or offset Royalties or exercise other remedies.
• If we pay you a Royalty on a sale and later issue a refund, return, or credit for that sale, we may offset the amount of the Royalty previously paid for the sale against future Royalties, or require you to remit that amount to us.
A written agreement solves all these little things up front so nobody gets weird later. I have had one with my co-author for years and even though some disputes are simply "flip a coin" to decide, it's served us well.