[[ Will it "just work" if I connect the one display to the Mac Mini (mini DisplayPort->Thunderbolt), then hook the second one up to the first one via DisplayPort? ]]
No, won't work.
I don't think the current version of the Mini can support "pass through" of the Displayport from one display to another.
You -can- hook up two Dell 24" displays to the Mini, BUT
- 1st one has to go through Displayport
- 2nd one has to go through HDMI.
Note:
It's -possible- that a new revision of the Mini -may- support Displayport pass-through. But that remains to be seen, if and when the new Mini appears...