As the child of a retired wildlife refuge manager, I have memories of attending Earth Day celebrations in the ’80s that featured Peter, Paul and Mary knock-offs singing about the answers and/or pollution blowing in the wind. I much prefer this alternative approach to earthy programming. The big stage in Centennial Park will host both Elizabeth Cook — who ranks among the best in town, or anywhere, at getting hilariously, grittily real in her songs (I refer once again to “Yes to Booty”) and her banter — and Mike Farris and the Roseland Rhythm Revue. The openers are the Nyama Drum and Dance Ensemble (a West African troupe that’s also part of the Global Education Center’s ethnically diverse lineup on the Youth Stage) and Billy Swayze. To top it all off, there’s valet parking for bicycles.