I am completely at a loss on Christmas ideas...help!?

Since you know them the best I'm sure you can come up with something that they would love. But if al else fails gift cards are the way to go. I personally love to get gift cards as a present. For the women maybe get a gift certificate for a spa or salon, even for your Fiance's Father and Stepmother, I'd bet they'd love a couples mage. For the groups a gift card for a restaurant and/or movie tickets. I'm sure whatever you decide will be great.