Son`s 16th Dinner Party

My son is 16 and we have him in private school and is having a dinner party at this restraunt where we have the garden booked and then later on into the party it is moved into another room we have reserved also. The party is only 3-4 hours but the problem is my sons afraid his friends will get bored and he wants something grown up and mature to do and his friends will enjoy. At first I told him a scavnger hunt and he said it was kind of semi formal so that didn`t work out(but maybe there is some kind of fancy scavenger hunt). My husband suggested a mystery game and he said it was an ok idea and if we couldn`t think of something they`d do that. If you have ANY ideas on what my son and his friends can do please reply
Thank you