Assuming you want to travel together, consider booking two one way tickets each to use your miles on different airlines. Start searching as soon as the awards are available (I believe UA is at 11 months prior). And just keep looking once a day. When you see something, book it.

Your dates are pretty specific. Flexibility is usually important. Willingness to arrive a day early or leave a day later can sometimes make all the difference.

There have been some decent paid fares to Europe recently, but you're unlikely to find deals this far out.

Finally, for specific advice on how to best use your miles, post in the respective airline forums here. People are generally glad to help with tricks and tools, but you'll get more expertise in those forums.