A release of liability may not be the best way to go. For members under age of 18, the parents/guardians would need to sign. How many would sign it after reading? It is not the best look to say 'sign here that you release us from liability if your kid gets injured or killed by our props'.
And even if the member signs, if there is a serious injury or a death it will be investigated by police in the jurisdiction the accident occurs in (see PR bus accident several years ago - was investigated by AZ police). It is possible that some sort of criminal negligence charges could be the result. The Corps and/or DCI's legal bill could add up quickly. Do the Corps / DCI have a contingency fund set aside for this?
And lawyers will tell you that even with a liability release legal action can result - once again, legal fees can accumulate quickly, and even if the Corps / DCI prevail the lawyers will still send a bill.
So, will liability insurance cover this? Perhaps, to a point. But insurance policies usually state that they won't cover losses to to negligence on the part of the insured.