I like Arlo from your boys list and all of your girls list (I haven't heard Avia before but it might be my favourite. If not, Isla).
Other ideas in a similar vein:
Austin, Artem, Aaron, Aidan, Brandon, Brennan, Carter, Callum, Conor, Cole, Caleb, Dylan, Dexter, Damon, Declan, Ethan, Ellis, Flynn, Fitch, Finn, Harley, Harvey, Harry, Hayden, Ivo, Inigo, Jude, Jared, Justin, Jordan, Jayden, Joel, Jake, Joe, Josh, Kai, Kayden, Kier, Liam, Luca, Logan, Mason, Morgan, Milo, Micah, Moses, Nico, Nathan, Owen, Parker, Preston, Riley, Rory, Rhys, Ryan, Saul, Solly, Seth, Tye, Tyler, Tyrone, Tian, Vinnie, Zach
Ava, Ada, Aya, Avery, Asia, Ayla, Aria, Anya, Amber, April, Aliya, Aphra, Bella, Bonnie, Ciara, Cleo, Coco, Callie, Cassie, Carrie, Connie, Dana, Demi, Daria, Daya, Dena, Della, Dulcie, Emmie, Eva, Ella, Erica, Erin, Eden, Etta, Enya, Effie, Freya, Fallon, Farrah, Gia, Gina, Halle, Honey, Ida, Inga, Irma, Iris, Ivy, India, Jayla, Jada, Josie, Jodi, Kayla, Kyla, Kyra, Kia, Kaya, Kyah, Layla, Lyla, Lyra, Lola, Leah, Lena, Lana, Lara, Libby, Lottie, Lexi, Lacey, Lois, Livia, Mia, Maia, Maya, Mila, Mina, Mala, Misty, Morgan, Macey, Miley, Marley, Maddie, Nia, Nyah, Nora, Nina, Orla, Pippa, Poppy, Posy, Penny, Peggy, Polly, Rosie, Rosa, Ruby, Romy, Rowan, Sylvie, Sadie, Sasha, Sienna, Tia, Thea, Tara, Tessa, Willa, Zoe, Zia, Zillah