I agree w/ the last post. Just because someone is now in high school doesn't mean they should be removed. granted your group makes that decision, but you would have more talent available is some young high schoolers were allowed to play. If there are too many guitarists in the high school group, I'd get some of the extras to help you guys out. You don't have to be in middle school to minister to middle schoolers!
You also commented about your mics. I'd check out
www.musiciansfriend.com. I order from there all the time. I've ordered 3 Nady star power 1 mics for $9.99 for my youth group. They sound pretty good and you can't beat the price!