I've done both.
Unlimited vacation doesn't translate to 13 weeks vacation. If the work has to get done then it gets done early or late as you said. Unlike teachers that will check out for the summer, (I know a LOT of teachers on Facebook that have posted about their next 6 weeks of wineries, poolside, books, and sleeping in), even your wife will work most of each week this summer. And you need to qualify the WAY more. Because she is contracted for more days so is she really making more or just working more calendar days? If she's making 25% more than you well, that's the other days she is expected to work. If she's making 50% more then we might be talking WAY for a little less work. Remember, you could work the next 4 weeks at summer school and probably make another 3k, maybe 4 if you really are offended about your unpaid time off.