I love the name Eden. If you really like it then I don't think you should let one child put you off, though I suppose you can't help how you feel. You'd also be able to uuse Edie for Eden instead of Edith.
Florence and Robin are very different names so you don't have to be tied to a particular name style. Maybe that's what's making it so hard for you - you could have literally anything.
Names in the same style as Florence without being 'too old fashioned' (as you said people in your area comment on it):
Astrid, Beatrix, Cassandra, Charlotte, Daisy, Eleanor, Evelyn, Francesca, Faith, Georgina, Grace, Harriet, Hope, Imogen, Juliet, Katherine, Lorelai, Lucy, Lily, Lydia, Matilda, Meredith, Nadia, Olivia, Philippa, Penelope, Ruby, Rosanna, Sylvia, Sophia, Tamara, Thalia, Verity, Victoria
Names in the same style as Robin:
Amber, Amy, Autumn, Alexis, Bronte, Carys, Cherry, Cleo, Darcey, Dulcie, Delphi, Erin, Elowen, Fern, Giselle, Heidi, Halle, Hazel, Ivy, Iris, Inez, Juno, Jenna, Katie, Kirsten, Lauren, Lois, Lena, Maeve, Nyah, Niamh, Orla, Phoebe, Polly, Quinn, Rosie, Romy, Rowan, Raven, Rivkah, Sadie, Summer, Scarlett, Skye, Seren, Tessa, Thea, Vashti, Veda, Willow, Wren, Xanthe, Zara, Zia
Names in the same style as Eden:
Aubrey, Avery, Addison, Blair, Briar, Cassidy, Casey, Everly, Ebony, Effie, Enya, Etta, Fallon, Genesis, Hadley, Hayley, Juniper, Kiki, Keltie, Keziah, Livia, Leah, Madison, Michaela, Nova, Nia, Paige, Piper, Riley, Reagan, Skylar, Sutton, Tansy, Taryn, Tegan, Zeryn