The answer to your question about bringing a civil claim against the people who attacked you is yes. You can file a civil suit against them for assault, and for battery. These are intentional acts by them, and you are allowed to file suit to recover your damages. You need to check the time limits to bring such an action in your state.
As far as some sort of Victims Assistance, you need to check with your state. However, I would be surprised if they offer any financial help in a case where charges have not been filed. You may want to ask about having a restraining order entered against the attackers, to have a court order in place so that if they do come to your park, the police will have the authority to arrest them. Usually, you can seek such an injunction without charge. Call the Clerk of the Court in your area and ask them what steps you would need to take to obtain an injunction. If you don't have the ability to pay the normal filing fee, they may have a financial affidavit you can fill out, which will waive the filing fee for the injunction.
Sadly, if you are in constant fear, bringing a civil suit against your attackers, they may not care about any judgment you may get against them, and they may violate the law, and harass you even more.
Under Michigan law, the club is not responsible for the intentional acts of tresspassers. You could sue the perpetrators for assault and battery if you can identify them, but collectability is a problem. Years ago, Michigan had a "Crime Victims Compensation Fund" that paid a victim for their out of pocket expenses for injuries suffered during the commission of a crime. I don't know if the fund still exists or how to make use of it if it does. I recommend that you call the state of Michigan offices (or go to their website) and ask about it. Or, Google "Michigan Crime Victims Compensation". Good luck.
You can seek restitution under the Michigan Crime Victims Act. That law protects victims and provides for remedies within the criminal court. You have rights to be kept informed of your case's status and you may petition the court for expenses you've incurred as a result of the assault. The act is rather detailed but it does have some limitations. Consult with the prosecuting authority that handled your case.
You may also pursue a tort action for the intentional torts of assault and battery. I would advise finding a competent injury attorney in your area who can help you place a value on your injury and let you know whether a civil action is viable.