You could try putting four coordset commands together with semicolons, e.g. something like:

coordset #0 1,100; coordset #1 1,100; coordset #2 1,100; coordset #3 1,100

That should all be one line... the e-mail program may break it up.  You would substitute the model numbers of your morph trajectories and frame numbers as appropriate, and you could include other "coordset" options. 
<http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/coordset.html>

I'm not completely sure they would start simultaneously, but that's my best guess of what to try.