Congratulations on your bun in the oven!
Sylvie is elegant. I think of Sylvie Guillem, the awesome French ballerina.
Olive -- urgh, drab. She won't thank you for it. Do you like the V sound? Consider Veronica, Verona, Vanessa, Virginia, Venetia, Violet, Evangeline, all with cute nn. Or, if you like the great-granny vibe with a prominent L sound, there's Cecilia, Clarissa, Christobel, Lucinda, Lillian, Loretta, Amaryllis, Priscilla.
Poppy is a term of endearment for a grandfather, at least where I live. If you must have it, consider Penelope with Poppy as nn.