You've got enough names for both girls there (if you like them as well as your husband of course).
Lily-May and Isabelle
or
Lily Something and Isabelle May
Alternatively, I think Lily-May goes well with:
Alexa, Ava-Rose, Bailey, Bella, Casey, Chloe, Darcey, Ella-Rose, Eva, Gracie, Halle, India, Jasmine, Jade, Jessica, Kitty, Katie, Molly, Macey, Mia-Grace, Olivia, Phoebe, Ruby-Grace, Rosie-Jane, Sophie, Sienna, Tia-Louise, Tallulah, Willow, Zia
And Isabelle goes well with:
Amy, Abigail, Anna, Bryony, Charlotte, Eleanor, Evelyn, Felicity, Francesca, Grace, Georgia, Georgina, Harriet, Hannah, Juliet, Kathryn, Lauren, Matilda, Miranda, Melissa, Madeleine, Natalie, Natasha, Rebecca, Sophia, Tabitha, Verity, Victoria, Zara