Which way to spell our daughters name?

Sarah
My husband and I are currently going back and forth between Sylvie or Silvie? We are worried with a y sounds to childish but is that just us or what do you guys think? Bad part is someone we know already made us burp cloths and other things with her name Sylvie monogrammed on them.. Since they were gifts I don't want to ask her to change it but if we want it with an I instead I hate to not be able to use them.. Which way do you guys think sounds better? Sylvie or Silvie? If it matters her middle name is going to be McKenna. Thanks!