You won't be violating any copyright, because the issue of your concern is trademark, and not copyright infringement.
Unfortunately, the trademark "Pink Promise" is registered. Consequently, any use with subsidiary terms, such as "garden club" would be a clear infringement of the Pink Promise trademark, because an ordinary consumer could be easily confused as to the source or affiliation of a garden club apparently associated with the Pink Promise trademark.
You may be able to obtain a license from the registrant: Walgreen Co.,***** Deerfield IL 60015 -- especially if the activities of your organization are intended for only a local reach. If not, then I believe you may want to devise a different trademark, because Walgreen is a large organization, and it could easily afford to bring legal action to prevent you from using the Pink Promise trademark.
Note: You could simply reverse the terms, to read "Promise Pink," and you would not infringe on anyone's trademark. So, that's another option to consider.
I realize that my answer may not be exactly what you were hoping to read. However, under the circumstances, the best that I can do is to explain what the law is and is not, so that you can avoid expending valuable resources looking for answers that do not exist, and concentrate on the options that are actually available.
Please let me know if you require further clarification. And, please provide a positive feedback rating for my answer -- otherwise, I receive nothing for my efforts in your behalf.
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