Questions about medical expense tax deduction

I know its early, but it occurred to me today that this year's medical expenses are going to probably well exceed 10% of our AGI, and with mortgage interest on top of that, I should easily be able to itemize.

The big expenses will come from my 3-month-old son's surgery, which happens next week, and my wife's hospital bill from the birth (and emergency C-section), and an ER visit and follow-up treatments for my daughter that also occurred this year. Even with insurance, this is a five-figure amount that puts pretty easily above 10% AGI. But from what I've been reading, you can also deduct mileage for medical care at 23.5 cents per mile. This will end up being somewhat important, as my son's surgery is in New Orleans -- 140 miles there and back -- and for the rest of the year we'll likely be doing follow-up visits every 2 weeks.

On top of that, since I'm deducting medical expenses, I wanted to try to nickel and dime the more minor expenses from the year, particularly my monthly prescriptions. Unfortunately, I haven't exactly been keeping receipts up to this point.

Seems like this sort of deduction -- particularly the mileage -- is a red flag, especially considering that I've only been able itemize once in my lifetime.

What is considered proof of these expenses, such as mileage? Should I keep a mileage log, records of the surgery having been performed in New Orleans? Should I get some kind of paperwork from the doctor at each follow-up visit?

For prescription history, copayments, etc. under my insurance, I can access every last detail of that info in my blue cross account. Is that sufficient?