Never tried to book 4 award tickets before but I've been trying to burn a lot of accumulated points myself recently (J for 2) and would suggest you explore Zanzibar, since you mentioned Africa. There's a pretty cool looking Park Hyatt there (your Chase miles will transfer to Hyatt) with decent award availability and DAR is serviced by all of the higher end middle eastern carriers (Emirates, Etihad, Qatar).

I just checked United award availability for the heck of it in mid April and shockingly found 4 business saver seats IAD-DAR with one 3.5 hour stop in ADD on Ethiopia Airlines.

Germany should be perfectly feasible as well, including picturesque rail transport options to other central European cities where you can use your leftover MR and UR points for hotels.