If you do them together the dominate one needs to read a few stories like SD mentioned and then try to be the quiet passive one for the week. Your life my depend on it.
When I took my classes there was a wife/husband/son team. I'm sad to report the wife definitely didn't learn much due to this factor. Fortunately the son was old enough to know to ignore his father and learn anyway. lol.
My wife is taking them separately this summer, then I'm taking her to lake washington and making her recover me via life sling + tackle several times. Puget Sound is rather unforgiving in MOB situations.