holiday weekend would be your best bet. have your spouse to be start talking to the scheds guys and his on-wing (or on-line or whatever they call it there) as soon as possible. Missing systems classes/tests (the first month or so) is pretty much impossible. If you found a 3 day wknd, you could possibly turn it into a 4 (which I did, just to hit Spring Break, but then again, I was in pretty good, or as good as a JG student can be, with the ops/scheds guys).
Oh yeah, the Tactics portion of the syllabus has quite a few 'blank' days. Get the syllabus for his class as soon as you can and check the activities for that time frame. Fams/Fly flight phase can be counted on for a flight scheduled every day M-F. Now whether you actually get to fly that day or not...
Really, you should just try to do it before or after the FRS.