Just to add - if you do intend to use devices such as bubble, snow machines, make a note of the floor surface before commencement.
A DJ agency in the south east area which aimed services towards children's entertainment experienced a lot of grief as a result of one gig.
The younger audience at the function were sliding all over the place.
Thankfully, there were no serious accidents on the day but it didn't help with one or two attending adults sliding all over the place either, apparently.
The performing DJ also managed to slide across the floor to the amusement of the remaining kids and parents as he was de-rigging the disco.
He fractured his hip and thigh bone and couldn't honour the rest of his gigs for months, which is how I found out about the incident due to providing gig cover!
Please be careful.
Have said this before, there are all sorts of games you can introduce for interaction - age orientated, age suitable and do not require the DJ to physically become involved with the audience in our over the top political correct society.
From experience, for great success, the attention of all the kids needs to be grabbed in the first 5 minutes, or the rest of the function could drag / be hard work.
Too many games during the function or too much music will affect interest.
Refreshments need to be gauged, especially right after the first 5-10 minutes and during the function.
For the ideal birthday party, the function can be viewed as having two halves separated by 'a break' which is the food and cutting of the cake time / happy birthday to…. - to allow the adults to prepare the party bags. Again, gauge the function. You don't commence with an energetic 'mad' game after the food.
If you encourage the attending adults to interact and become involved, the kids will love it, the adults will have a good laugh and you will generate more bookings, without doubt especially in the second half.