1 dose of MMR has a 95% chance of working. The regular schedule, however, calls for two doses (at least 1 month apart) in order to increase that effectiveness to 98%. I don't think that second dose is necessary though - one should be fine.
As for Cpox, 1 dose is 85% to 95% effective. A second dose, at least 3 months apart, is the basic recommendation. But in my opinion, 1 dose works well enough. If he did end up catching Cpox, the vaccine would likely make it a mild case anyway. But if you want more guaranteed protection, you'd get both doses.
I'd separate the MMR and Cpox by a year.