I like the idea of taking along a blanket to drape over the lap while pedaling these things. Might I also suggest getting leggings just to be on the safe side, too? (There are also sports skirts that have leggings sewn in, but I’ve never tried them so I can’t guarantee that they solve all the issues they’re trying to remedy.)
And I must say, in any case, riding a regular bicycle in most of the skirts made available to us is no fun. If a skirt’s too narrow at the knees, one can’t pedal, modestly or not, at all. Too loose and flared out, though, and the hem gets caught in the gears.