unless you're playing in the middle of a large city you're not gonna get shot by a cop (and if you are playing the the middle of a large city, you're dumb), they dont shoot first ask later (esp when they see a bunch of kids aiming guns at eachother that the general public has no means of attaining). We played 3months after 9/11, so some lady just freaked out. We returned later and the cops didnt even really check the area out (they didnt run after us with guns drawn, if thats what you guys got out of it, we just ran away), just talked to the lady, not to mention most cops use airsoft as training. That incident was more our stupidity, as opposed to anything else (we didnt see the.....um....no trespassing sign.....yeah)
Its really all up to preferance i suppose, paintball is just a little too mainstream for me. In my opinion it doesnt matter which one you play, you're still gonna find nutjobs who take things too seriously. If you get a good group of friends (half the time i only play with 3-5 other friends) its more than enough, and you dont have anything stupid going on (using marbles or frozen paintballs). I spent 300 bucks for everything ive needed so far, and no more than 20 on ammo in the last year and a half, and we played once or so a week. Ive played both paintball and airsoft, and from experience i can say paintball is a lot more painful, though in paintball you are less likely to get hit several times in a row (my AK fires at about 13-15rps, so you can generally expect to get hit 5-10 times if you're unlucky). I also used to live in the woods, and thats where me and my friends would play. There isnt any need for a feild or reffs, mainly because there isnt anything to worry about as far as muzzel speed, frozen paintballs, or in the parents case; staining everything with paint. Airsoft is almost the same, you still have to wear the masks and generally some long pants and a longsleave t-shirt; its just as safe. The great part is that you can wear shorts and a t if you want, and you wont have a billion massive bruses all over. It will hurt a bit more (like a bee sting), but airsoft just seems a bit more versatile
if your kids are just gonna shoot trees, cans, and stuff i think they'd like an airsoft gun, it just looks so much cooler. Airsoft is generally safer, and so much easier to maintain and start with too, I dont know how many kids i know that have switched over to airsoft.
basically, it all comes down to a personal preference; mine goes to airsoft, someone elses to paintball, and in most cases; its a general weird look to the whole concept of shooting someone for a sport, followed by an insult of how wierd you are for playing......we would get that one a lot