The best insurance for an archery range is through the ASA. For $350 a year he gets a million $ liability insurance. The real bargain is that for that $350 he will get 10 ASA individual memberships he can sell at $30 each. That makes a year of archery-specific coverage only $50. No one can touch that!
Tell him tp get on line the ASA web site and find the contact information for his state rep.