I have to show my idiot card here as I'm a studio guy and don't really have the experience with wireless systems that most of you do. My parents are administrators at a large school in Indonesia (Only mentioning that in case there are any unique obstacles in that country in regards to frequency considerations) and I'm trying to help them out long distance. The school would like to buy a large wireless system for stage productions the kids will be doing and want 20-25 wireless units that could all be used at once.
I'm looking for some advise at what systems to look at that can handle that many units running at once. As far as I know they have no A/V staff (or no one there that knows much about sound), so the easier to set up and run (IE "idiot proof") the better. It would be ideal to have a package that includes transmitters, receivers and headset mic of some sort (They have specifically requested headsets and not lapel. http://amthanhthudo.com/loa-line-array Something more conspicuous like the countryman's would be great). Budget shouldn't be a concern. I told them off the top of my head to be prepared to spend around $20K and they didn't seem too concerned.
$20,000 is a nice start but nowhere near what you'll need to spend to get a really good system installed. Forget about a "plug & play" setup with the complexity of what's required. You'll need a dedicated person to handle the set up, running the equipment and doing the required maintenance and yes there will be required maintenance. I would suggest that you or your parents look for sound contractors as close to Indonesia as possible and ask them for their assistance.