I think the dedicated shadowing of a CRNA is great. Mentioning that you worked in the OR for 5 years is ok because it says you know OR rhythm, but those skills don't translate into CRNA skills so I wouldn't linger too much on that. Make sure to really emphasize and be confident in your ICU knowledge. They are looking for expert ICU nurses to turn into CRNAs. The best way of doing that is getting a certification, like CCRN or TNCC. As far as grades, if you get an interview before retaking them, make sure you know WHY they were lower. It's ok to say you were working too much to study as much as you'd like. Of course, the follow up question would be if you plan on working during CRNA school. And you can say through your undergrad experience, you've learned your lesson and you would not. Another follow up question would ask if you felt financially stable giving up work for 2.5 years.
If you don't get an interview, in addition to retaking classes, I would suggest getting into a cardiovascular ICU because they work more with hemodynamics. Next to airway management, CRNA is all about hemodynamics management. (As a side note, that's why your OR experience isn't a strong asset to your application- you didn't manage the ABCs of the patient. It's not bad, but it's not strong experience either) You of course are required to have ACLS PALS and BLS certification as part of your application, but if you don't get selected to interview this first time, you could consider working in a NICU or, preferably, PICU. Basically, if not picked for an interview this time, make a drastic change to improve your application and reapply next year. This not only shows persistence, but also drive.