I say ivory! I am having the same problem trying to find shoes to go with coral dresses and think the silver makes the dress look cheap. You can always go with a dyeable shoe you like and see what colors they recommend at the bridal shop to dye it in!
Have you thought about an antique gold? Not a bright gold. A softer deeper tone. It would be in the same family as the champaign and would look nice with the wine.
You also go just go with the champaign.
Incidentally if you have floor length dresses you might want to consider just letting them wear whatever. No one will see their shoes anyways, I did this for my bridesmaids. Honestly no one could even see their shoes till the dancing started. And by then who cares what color the shoes are.
Not that there is something wrong with picking a color. Just giving an extra option.