I'd like to launch them all to say, Jupiter, at the same time, but I have a feeling with their different Isp's the fleet is going to rapidly break up.
Explorer looks cool, will have to try it out.
Would be interesting to see if you could time their arrivals so they all converged on Jupiter at or near the same exact MJD. That would be pretty cool, maybe. Maybe not, unless you aligned and synced their orbits immediately after arrival...would be tedious at best. On second thought, maybe get them all there in due time and then rendezvous later.