The director Tina Landau knows firsthand how much the New York City waterfront has changed over the decades. In 1996, she did a production of Charles Mee’s “The Trojan Women: A Love Story” at the East River Park Amphitheater. “I remember going there, and we cleaned up syringes and condoms,” Landau said.She was speaking backstage at another riverside amphitheater, albeit in much improved conditions: at the public park Little Island in Manhattan, which opened last year at Pier 55 on the Hudson and where Landau is directing “The Big Mix,” a new performing arts festival through July 3. The roster features prominent names like Idina Menzel, Tonya Pinkins and Peppermint alongside poets and fire artists, neighborhood dance troupes and choirs, tap dancers and marching bands.“I wanted to focus on representation of as many kinds and types and ethnicities and abilities and genders,” Landau said.One of Little Island’s four artists in residence, Landau has come a long way since her days picking up trash before a show; she’s a member of the Steppenwolf Theater Company in Chicago, and was a Tony nominee for “SpongeBob SquarePants: The Broadway Musical.” But the inspiration behind “The Big Mix” came not so much from a high concept as from simply looking at the calendar.“I saw that Pride weekend was a week after Juneteenth and a week before July 4th,” Landau said. “I started thinking about what these holidays are: What do they mean to different people, and why do we celebrate them? So each show is in honor of, and an interrogation of, the holiday that falls on that weekend.”While she takes seriously the meaning of these commemorations, Landau also wants to entertain. “Let’s get a ton of different people in here and mash them up, and let it be sloppy and crazy and big and powerful and fun,” she said.From left, Zach McNally, Ianne Fields Stewart, Allan K. Washington and Marla Louissaint rehearsing at Little Island for a Pride Week performance. Vincent Tullo for The New York TimesJoshua Henry (“Carousel,” “Waitress” and the upcoming Broadway run of “Into the Woods”) is the M.C. of the Juneteenth celebration, running through Sunday, with a lineup that includes Pinkins, the singer Mykal Kilgore, the Sing Harlem Choir and the dancer Brinae Ali. Henry is fully on board with Landau’s big-tent approach.“It’s my job to make sure everyone’s having a great time,” he said in a video chat. “As I become more active on social media, people are starting to see my personality more, and I guess I come across as a fun-loving guy, which is pretty accurate,” he added, chuckling.Henry also suggested potential guests to Landau, who was all ears. “I wanted to find a way to turn over the space to voices other than my own,” she said. “For Juneteenth, for instance, I’ve invited people, but I’ve also been very open to what they want to say and how they want to say it. We’re in a very charged and thankfully transformative time, culturally.”The L.G.B.T.Q. Pride program (June 23-25) provided Landau an opportunity for some course-correction, decades after her 1994 show “Stonewall, Night Variations,” which also happened to be on a New York pier. Looking back on that show, Landau believed it wasn’t as inclusive as it should have been — leaving out people of color, homeless youth and transgender women in particular, who were all “part of that moment in time.” This time around, she said, “I wanted to honor those that I, in some way, had left out.”That’s why Peppermint, the “RuPaul’s Drag Race” runner-up, seemed like a great addition as M.C. But because she could host only a couple of the Pride shows, Landau turned to the costume designer and activist Qween Jean to handle the other two. “I had been following her, and I thought, ‘She’s the real deal, she’s out there doing the work,’” she said.Another participant in the Pride celebration is the choreographer James Alsop, who had been wanting to collaborate with Landau since meeting her in 2019. “She could have said, ‘I have a sneaker full of poop,’ and I’d be like, ‘I’ll choreograph it!’” Alsop said with a laugh.Fortunately, the director had a better offer — to choreograph a group number to Diana Ross’s “I’m Coming Out” for the festival, despite being deep in rehearsal for “The Devil Wears Prada: The Musical,” which premieres next month in Chicago.Jose Llana, right, and Brandon Contreras rehearsing a duet in front of an unbeatable backdrop, the Hudson River.Vincent Tullo for The New York TimesOne challenge was to concentrate on the dancing and not the spectacular vista right behind the stage. “Let the backdrop do what it does and just be beautiful, and let me not think too much about it, because then I won’t really focus on the movement and the dance and the joy that I want the audience to feel,” Alsop said. “I just want to exude nothing but radiance and light.”Rounding out the festival is the Independence Day show (June 30-July 3), hosted by Faith Prince — a beloved Broadway star who won a Tony for “Guys and Dolls” in 1992 and starred in Landau’s revival of “Bells Are Ringing” about a decade later.At first, though, the actress worried that she wouldn’t be a good pick for the diverse group of performers, which includes the samba-reggae marching band Fogo Azul NYC, the poet Denice Frohman and the Heidi Latsky Dance company.“Tina said, ‘Oh no, you’re quirky in your own way,’” Prince said on the phone. “And I said, ‘Yeah, I have age on me, which is another factor.’ Just when you think you’re in your prime, they want to put you out to pasture!”Prince is familiar with at least one of the performers in the Independence Day show, the Broadway regular Judy Kuhn, but she’s particularly excited by the mix of professional artists and community members, similar to the approach in a production of “The Tempest” she co-directed at the Tulsa Performing Arts Center in 2019.“We used a lot of different groups around the city, and it was thrilling,” Prince said. “It brought so many different communities together, and they were all cheering for each other. I’m really excited that’s what will happen here.”The Big MixThrough July 3 at Little Island, Pier 55, Manhattan; littleisland.org. More