The City of Milford, DE has the following ordinance:
§ 190-2. - Smoking prohibited.
(1) Smoking shall be prohibited at all times in all City of Milford public parks and playgrounds, including, without limitation:
a. Banneker Park
b. Bicentennial Park
c. Marshall Pond Park
d. Marvel Square Park
e. Memorial Park South
f. Tony Silicato Memorial Park
g. Library Square
h. Milford Library Amphitheater
i. Goat Island
j. Mispillion Riverwalk
k. Milford Dog Park
B. Smoking is prohibited at all parks and playground areas owned by the city and open to the public.
a. Land owned by the City of Milford and used by Milford Little League. Policy will be established and enforced by Milford Little League Board of Directors and/or designee.
C. Smoking is prohibited in a building or open-air facility owned, leased or operated by the City of Milford.
Signs are posted and compliance has generally been good. The primary issue has been with cigarette butt litter.
While I was City Manager in Oberlin, OH we adopted this ordinance that focused on the areas where people - particularly youth - would gather:
927.29 SMOKING AND TOBACCO.
(a) Smoking , as defined in Chapter 506, of the Codified Ordinances, and the use of smokeless tobacco products is hereby prohibited in any areas of any Oberlin Park , as defined in Section 927.00, as may be established by the City Manager as non-smoking and tobacco-free zones.
(1) No person found to be smoking or using smokeless tobacco products in such designated non-smoking and tobacco-free zones in a park shall fail to immediately cease said activity when requested to do so by City staff, a Police Officer, or a person charged with the management, operation or care of any City-owned park , including any baseball or softball umpire or soccer official.
(2) Should a person found to be smoking or using smokeless tobacco products in a non-smoking and tobacco free zone in a park not immediately cease said activity when requested to do so, as described in subsection (a)(1) hereof, he or she shall be guilty of a minor misdemeanor.
(3) Persons who repeatedly violate this section, may be permanently banned from City Parks .
(4) Lack of intent to violate a provision of this chapter shall not be a defense to a violation.
(b) At least one sign informing the public of the ban shall be placed at the entrance of each such non-smoking and tobacco-free zone established by the City Manager. Notice shall also be placed at such location(s) within each park designated for notices and information, and shall be included in appropriate forms, documents and other materials provided to residents and others when reserving park facilities or space.
The codified ordinances for both cities are online if you need to refer to other sections.