My boy turned 14 over the summer, and for the past several years his birthday celebrations have been relatively low key. He invites a handful of boys over, I order pizza and bake a cake. They eat, play on the PS3 and play Nerf wars then we all go to a matinee. Once back at the house the cycle starts all over again. LOL
I usually have the boys come over between noon and 1 and bring the ones not staying over for the night home by 7pm.
Check with your son - at this age they have definitely have an idea of what they want to do for their birthdays.
Don't forget to schedule a special birthday boy hug for him. I also like to surprise mine with Breakfast in bed for his special day.