Jasper,
I've added a new function (you requested and implemented in xfce4) to
mcs-client.h to check and spawn a mcs-manager
gboolean mcs_client_check_manager(Display * display, int screen);
Requires checking libxfce4mcs > 0.0.2 in your configure.in
Cheers,
--
Olivier Fourdan <fourdan at xfce.org>
http://www.xfce.org