If the adds are links or otherwise non-privacy invasive (i.e. without access to your ip address and browser info) then the ads would be all right and if your plugin is good and I can be assured of privacy, I will even attempt to support your advertisers. But only if I can be assured they will not be data-mining in any way - and that you will not invade the privacy of users of the plugin.
I am one of the many who use 'free' services to avoid the privacy invasion inherent in paid-for internet services. I don't have a problem with paying but resent any data mining.
Please put a unambiguous non-squirmy clear statement of any privacy implications of using your plugin on your website.
I would also be more than happy to buy you that cup of coffee, but not if it compromised the privacy of my internet browsing.