12 Yr Old Girl`s Capture The Flag Party

I am planning an October birthday party and thinking of doing capture the flag for about 30 boys and girls. Our parties have always been a big hit in the past so I want to make it special. I have never had more than 10 girls for any of the past parties nor have I done co-ed before. I am thinking of dog tags as either favors or invites and/or personalized t-shirts for the two teams. I don`t want to spend an obnoxious amount but would love feedback on any creative ideas for the party from invites to favors to extra touches. Thanks!