Applying to 1st round or 2nd round

The first round isn't necessary the "top-tier" round. In fact, the second round is often a bit more competitive just because more people typically apply. But, generally, there isn't a big difference for either the first or second round--as long as you apply before the third (or the last round, if it's different), your chances should be about the same. If you already know where you want to apply, I think you should be able to bust out your applications for Round 1. Trust me, it'll be really nice if you have an acceptance before the holidays

Also, your GPA may not be fantastic, but it's also not terrible. Since you're an older candidate, the adcoms will probably focus more on your work experience than your grades. I think you should be fine as long as you put together strong applications. That said, make sure to use the optional essay to (briefly) discuss the reason for any low grades, if you have a good one (e.g. illness, death in the family, etc.). If you had a low GMAT quant score and/or low grades in quant-related courses, this might be a good time to consider a summer math course.