I'd do the first attempt around finals. I think it would less directly affect any sway (if at all). Being relaxed on vacation would be great, but if you can't stick to diet (who would want to!!), I'd go with the earlier attempt. I wouldn't push anything off either, your sway is strong and over the next two months, you'll be making it second nature, so I bet you won't be thinking much about it at finals time.
I am facing a similar decision though, so I know it tough to decide! We either try in late-June (but I don't really want a Feb baby, I deliver 3ish weeks early) or in late-July (after a trip in early-July where I absolutely won't do diet). I haven't decided yet. But I'll have to think about it soon enough.