you don't have to tell them the reasons why you put the pieces in a certain order. if you have a rehearsal - you can get a better idea of who should be placed where. if you do it according to ability, you'll sustain interest better. i've watched a lot of conductors and they never make it a conversation piece. they just listen, write down the order, and print out the program. people usually go where you place them and if you have to make a slight change to accomodate someone (that's ok) but usually people don't argue if you just take charge (especially since you were asked to).canon in d is pretty well known - so maybe it's a good start already? wouldn't start with a fugue. (*you could put some notes in your program if you had time) and a few musical terms in german at the back of the program just for fun?