get some ideas with dry ice probably would be cool. Perhaps a bluelight for glow in the dark things, test tubes with candy, cool fake glasses, magnifying glasses to use with a game. Mousse to spike the hair of the guest, or your son. Hair paint for effect, maybe green or blue.........Find a cool simple experiement and cool gift for gift bags.
Here is the only site you will need. I used this not only for a party, but for experiments for my 11 year old who I home school as well. His entire room has a mad scientist kind of feel. They have great easy ideas.
Our favorite what you can do with dry ice. You may want to search that topic if it isnt listed inder the party ideas. Have fun.