I'd recommend getting a heavier weight than .2
Read this http://www.airsoft-forums.co.uk/index.php/topic/30324-bb-weight-vs-distance-comparison-proof/#entry235297
Throw them away and buy some DECENT BBs especially for your first skirmish as they'll affect your accuracy and may shatter on impact. Devils and blasters can be bought cheaply from pretty much every reliable airsoft retailer.
The sun would have fun with taking what you just said out of context
Nah 1500 old men and geeky guys that haven't showered in a few days is a no go for me.
Think it's a good idea but don't spam the second hand sales with brand new stuff and if you do make sure it's a decent deal, maybe talk to one of the mods about sponsorship (like tiger111hk or asp)