I've been hosting kids tournaments for about 2 years now.
When possible, I try to give "awards" to all participants. Crown Awards has an inexpensive crossed-swords pin that is great for this.
I generally give a short talk/demo to the parents before each event (especially the younger events). Many parents have never seen fencing before, and don't know how to interpret the lights, what the ref does, etc.
The format I've found that works really well is to do a round of pools, then another randomized round of pools, and then take the top 4 fencers up to a DE finals. This gives everyone lots of fencing (8-10 bouts is generally plenty for kids 7-10 years old). The very short DE allows everyone to stick around for the exciting conclusion, and to be there for the awards. A long DE means that parents pack up and leave....
The kid-friendly referees are a MUST. The rules must be consistently applied. If the ref's (as a group) decide to suspend a rule (e.g. shim/weight tests) this should be announced and handled consistently. NO SAFETY RULES should be ignored!
A weapon is a device for making your enemy change his mind. The mind is the first and final battleground, the stuff in between is just noise.
L.M. Bujold