Is it excessive to hire a DJ for my sons high school graduation party?
Not at all if the party will be large and entertainment is needed. You don’t necessarily have to hire a pricey professional DJ. Consider a less expensive freelancer or someone who’s just getting started and needs to build a work history. You could even ask your son’s friends to see if any one of them would be interested and have the equipment to do this. Otherwise, rent or obtain some larger speakers and you can "DJ" the party yourself with your iPod by playing cool tunes to dance to.
