Keep it simple - live off the course. Do not complicate your day.
You do realize you're posting on a message board of neurotic triathletes, right?
Hey - I resemble that remark! It took me time, but I carry so little stuff to the race . . . and usually arrive somewhat late. Perhaps it is my simple mind. David * Ironman for Life! (Blog) * IM Everyday Hero Video * Daggett Shuler Law * Disclaimer: I have personal and professional relationships with many athletes, vendors, and organizations in the triathlon world.
SN1- extra tube and C02 (since I have 808s and need a removable valve which they don't always have on course); extra gels and salt table because I have a tendency to accidentally drop things. A JIC Zantac (my stomach hates me).
SN2- JIC Zantac and Imodium (once again, my stomach hates me).
I never plan on stopping for special needs bags and a lot of times...never do. But I like having some emergency stuff in there just in case things don't go my way.
I LOVE the prior idea of the gift cards! Never thought of that....
You need tubes with a removable valve. I buy these off Amazon: Continental Race 28 700c x 18-25 Bike Tubes (5 Pack) - 60mm Presta Valve. You also need valve extensions and a little wrench to take the valve off and on. Sometimes the rental wheels come with the annoying extension (one without the valve) so I would recommend buying the good ones before you go. Note: I carry both types with me just in case I need to borrow a normal spare instead. I have pasted examples below so you can see what they generally look like.
Something that would've helped me a ton in Louisville and might be relevant in TX because of the crazy storm two years ago and last year's cold front is to keep some cheap gloves and a garbage bag fashioned into a poncho in your run special needs. Freezing my ass off slowed me down a lot.