You won't be giving blood per se on I day; but yes the medical's will take some blood.
That being said...realize when you donate a pint of blood you're then restricted from donating again for something like 56 days. Personally...while I applaud your interest, this close to I Day...I don't think I'd do it. It takes time to replace that pint in your blood stream. The Red Cross says the body takes 4-6 weeks to replace the red blood cells you donated. Okay...you're going to be short a BUNCH due to the altitude issues you'll have...I don't think I'd make it worse.
Once you're accepted into the Wing...if you still would like to be a donor (I was for years, its a great way to give back) then see if there are any restrictions and if not: go for it! It's a life saving item that too many people won't do.
Steve
USAFA ALO
USAFA '83