Ideas for 7 yr old birthday!

I am trying to figure out some original ideas for B's birthday coming up. It is his golden birthday, turning 7 on the 7th. We are having it at a nature center where they will spend the first hour outside (if it gets above freezing), and the 2nd hour inside doing cake/gifts/games etc. I was thinking of doing something for the goodie bags that involve it being his golden birthday but can't think of anything cool. I will have 12 boys and 3 girls. (he wanted to invite 2 girls from school, how cute is that?!) I want goodie bags that are unisex. My first idea was to get those golden dollar coins and put a little note that said "thank you for coming to my golden birthday" along with some other little toy or ???? But then I looked online and realized they cost way more than $1 a piece and so that would add up. I could go to all the banks around and try to find the coins but do I really want to do that???? I think it would be cool, but not worth the effort really. I don't want the typical candy/junky plastic toy goodie bag. I want something they will really use. Maybe a coupon for ice cream or ???? I have no clue. Something useful, practical, but still fun. I just hate to give out stuff that will be thrown out. I also need a quick game we can do if we have time after all the other activities. Something that 14 seven year olds will think is fun. I am finding that the older they get, the harder to keep them interested. They have longer attention spans but more expectations. I was thinking something they can make or an activity or game of some sort. I have to figure out the cake, plates/decorations, and that is about it. Thank god I'm not doing it at home!!! So excited about that!