When my son turned 4, we had a joint birthday party  for both him and his pre-school friend who has a  birthday a week earlier.  My son was into the Olympics at the time, and his friend was a Dinosaur fanatic, so we came up with a "Dinolympics" theme to satisfy  them both.  Because we had almost 30 kids as  guests, we chose a park location and divided them into 4 teams.  Each birthday boy chose 2 favorite  dinos and colors, hence the teams were blue  pteranadons, yellow triceratops, red allosuruses, and  green carnotaurs. I scanned or downloaded from the  internet a picture of each of these dinosaurs, format- ted it for a sheet of large address labels, and printed  it in its team's color. As each child arrived, he or she  was given a label marking him or her as a member of a particular team. ( I also used the computer images to decorate plain paper lunch bags which we used as  goodie bags.) One of the birthday boys had an  8-year-old sister, and she, 2 of her friends, and a ten-year old party guest who had been consulted ahead of time acted as team captains, leading the  party goers through a relay Dino egg and spoon race and a pull the other team into the lava pit (red  sheet) tug-of-war.  We also had a hunt for dino  food--each team was given a grocery bag and sent to  look for practice golf balls tied with the ribbon color corresponding to their team color--the team that found their twelve "dino snacks "first won. The  follow-up to this was a game of "feed the dino" in  which the first team to throw all its balls into a dino  mouth (artfully constructed by my son's uncle of corrugated cardboard, hot glue, and tissue paper)  won.  We finished with a game of pin the tail on the  (down-loaded image of a) carnotaur, and a T-rex  pinata. After all of the games, we played the Olympic march on a boom box, lined the kids up and the team captains put medals around their necks.  We bought   most of the medals ( and most of the party favors such as dino masks, temp tattoos, miniature dinos, dino finger puppets, etc.) on-line at Oriental  Trading Company .  However, my son insisted on a "large medal with blue" on it. So we constructed his  and the other honoree's out of craft-store gold foil stuck  to cardboard with a doublesided sheet of  adhesive with a sparkly blue craft adhesive circle in the middle, decorated with stickers and stars, and  suspended from red, white, and, blue ribbon. The  boys were thrilled with their special medals. For food we served hot lava (chili) and rocks (cornbread),  bones (bowtie pasta,  treetops (green salad), and  sticks (breadsticks). Instead of a cake, I made  cupcakes, each decorated with  green frosting, coconut flakes dyed green like grass with food  coloring, and a small plastic dinosaur on top.  The kids got to keep their dinosaur along with their gold  medal and goodie bag treats.  For the birthday boys, I made two cakes in small loaf pans, sculpted them to  resemble volcanoes, frosted them with brown frosting, and used red and orange frosting spouting out the middle and over the sides, and of course the  candles were lit in the volcano tops. I placed each at the edge of its own 10x10 square of cardboard lightly  frosted with green frosting from the cupcakes and placed a plastic tree, a plastic dino, and a plastic nest of dino eggs in the green frosting and let the frosting  dry.  All the kids were winners and had great fun.