You may already know this little tip, but it has been extremely helpful to us. We've been putting witch hazel on our mosquito bites within 30 minutes of getting the bite (the sooner, the better). It literally causes the bite to disappear, though not instantly. I got 3 big bites on my ankles last night. After applying the witch hazel, I completely forgot about them. When I remembered to check them several hours later, I couldn't even find where the bites had been!
Our bottle isn't anything special. I think it cost around $3 for 16 fl. oz. It looks like a bottle of rubbing alcohol and says, "distilled extract of witch hazel." I bought mine at Whole Foods, but I know I've seen it at Kroger in the first aid section. It's also supposed to be good to put on minor cuts and scrapes, although we haven't tried it for those purposes yet.
I hope this will help you and your kids have a more pleasant outdoor experience this spring and summer!