Okay, it's a Tucson municipal ordinance, not a state law. Thanks.
Tucson Code § 7-481(b) requires that you post the following at your establishment, and provide a copy to each purchaser.
Under Tucson Code § 7-481(b), operation of motorized bicycle or tricycle is prohibited:
For persons under sixteen (16) years of age.
On any public sidewalks, multi-use path, and shared use path and on any designated pedestrian path in any public park.
For persons under eighteen (18) years of age unless the person is wearing a properly fitted and fastened bicycle helmet which meets the current standards of the American National Standards Institute for protective headgear.
At night unless the motorized bicycle or tricycle has a lamp and red rear reflector.
Also, a motorized bicycle or tricycle operated in excess of nineteen (19) miles per hour is regulated by state law and must comply with state law requirements.
Okay, so much for that part. As for your release, what you may want to consider is taking all of Sections 5-4 through 5-11 and Section 20-29, compiling it in a single document, along with the previously-quoted required disclosure, and then placing at the bottom of the document, something like:
"I hereby acknowledge that I have received, read and understand, this copy of the Tucson Municipal Code Sections concerning the operation of a "motorized bicycle," and that in partial consideration for NAMEOFBUSINESS' provision of labor and materials on my behalf, I hereby release NAMEOFBUSINSS, its agents, affiliates successors and assigns, from any and all liability for damage or injury caused to me, my property or to any third party, in connection with my use of the labor and materials provided.
Printed name, address, etc.
Note: the above is no guarantee of immunity from liability. Courts disfavor such prospective liability releases, because the purchaser cannot reasonably contemplate in advance all of the reasonably foreseeable injuries that may be sustained.
Thus, as with any business, the only real means of protecting oneself, it through the purchase of liability insurance, and the formation of a corporate or LLC entity under which to operate the enterprise.
And, at this point, we're out of scope for the question. But, if you want to get this "just right," you are strongly advised to obtain local legal representation and have all of the final documents professionally drafted and reviewed.
I wish you the best.