I can't speak for all the cities you mention, but I know at least in Paris and Venice that Priority Club works for two parents and two children in theory. By that I mean it comes up with results, but whether it will let you click through to actually book them I can't say for sure as I don't currently have enough PC points to try. In general I think that Priority Club seems to have a more family friendly take on max # of occupants.
I have done a few posts on a few different chains on this topic. Here is one to the PC post.
http://boardingarea.com/blogs/mommyp...priority-club/
Another potential program to consider is Club Carlson as their "non-standard" rooms are sometimes a very reasonable additional points price.