If you can avoid it at the moment I wouldn't mix them especially if they haven't been together before. It does very much depend upon the other mares - have they had babies themselves, do they stick together as a tight group, is one of them clearly the 'main' mare?
If you do put Raven with them, there is a risk that they will all want to speak to/sniff the foal. The foal can get worried and run off, then chased by Momma who is now stressed about baby's safety, then followed by the 'herd' who still want to say hello. This can really lead to a panic situation (and is extremely difficult to sort out/stop happening) and give you a very exhausted baby!
If you do anything at all then I would be slowly adding one mare at a time to Raven's paddock to keep the introductions slow and under your control. Or wait until Sweetie foals and just keep the two girls together for a while, before adding the other mares slowly into the mix.
If your other pasture is really large then just think how impossible it will be for you to run round trying to catch Raven, let alone the foal, should things not work out and the 'chase round' begins.
JMO but I wouldn't chance it.