airsoft guns, similar guns

Question
 Are they safe?  How powerful are they?  Where would we use them?  Can we use them in our back yard?  Where can I find good information about them?  Would it be something appropriate for me to do with my 11 year old son?  If there is something more appropriate, can you tell me what it is?   Are there tournaments with these guns?

Answer
I'm proud to say this is something I know quite a bit about - I am the Safety Officer and an executive member of the Minnesota Airsoft Association.

Airsoft guns fire a plastic 6mm BB at a velocity of around 280 feet/second.  This is slower than most .177 BB guns.  However, they have plenty of power, with an effective range of about 100 feet.  When shooting Airsoft guns, eye protection is mandatory, and you want to observe all safety rules you would use with real or BB guns:

1. Treat all guns as if they are loaded.
2. Never point the gun at anything you do not wish to shoot.
3. Be aware of your target and what's beyond it.
4. Keep your finger off the trigger until you are on target and ready to fire.

You should be able to shoot an Airsoft gun anywhere you can safetly fire a BB gun - but make sure you check your local laws first.  Because of their realism, some states have special laws covering airsoft guns.  

For an 11 year old, Airsoft is just as safe as a BB gun, but for someone that age, adult supervision would be a must.  I can't speak for every state, but here in Minnesota, you have to be 14 to posess an airgun (airsoft or otherwise).  

Airsoft guns are used in two basic types of competition.  First and most common is "skirmishing."  This is a combat simulation, similar to paintball, where players shoot at each other (while wearing eye protection and other protective gear).  Unlike paintball, there is no paint to determine if you are hit - it's completely honor-based.

Airsoft guns are also used in target competition.  There is BBIPSC, which is a form of IPSC shooting, using Airsoft pistols.  Airsoft rifles are also used in CMP-style shooting events.  Most Airsoft target shoots I know of are amatuer events.  

For more information, please check out the Airsoft Safety Manual I wrote for the MAA at www.mnairsoft.com.  You can also find out more info about the Airsoft hobby there.  

I hope this answers your question.  Please drop me a line if you need more info.