Informal silhouette matches - any pointers?

[Kragman1]

I plan to pick up a dozen of the little airgun silhouette sets ("Slynger" brand) to use for fun 1-on-1 "matches" with my girlfriend and foster brother.  Both are new, both enjoy it, and I'd like to keep them enjoying it!

So I plan to set up at 20, 30, 36 & 45 yards, 1 "racks" of 5 targets per person at each distance. 
I'll allow either 2 or 3 minutes per rack with a little timer.  Whatever works out to enough time, but with a little excitement...
I'll set the targets at the back of a board but the must fall.  All or nothing deal.
I'll allow a shooter 5 pellets to be used per rack, at any targets they like.
If they inadvertently knock over a target they weren't shooting at, it can't be scored or reset.

Or at least thats the plan.  If anyone can critique and/or add to the above I would appreciate it.  Just keep in mind that its being done for new shooter fun.  And its only the three of us for now, so competitive enough to be engaging and make some laughs.  Not hard core, and I don't have to worry about every little loophole because I'm not managing a fiesty crowd!  lol

Thanks in advance!