Unless the order outlines a "reset" (and most don't), you just continue following the order. Eventually, there will be a month in which Mom gets three weekends in a row, and it evens out.
That said, in an every other week plan such as what you're working towards, ALSO allocating breaks / long weekends that aren't really holidays can get quite unwieldy. It's much easier, IMO, to worry about the "big" holidays - whatever those might be for your family - and let the visitation fall where it may on the "small" ones.