Allyson,
First of all, congratulations!
To begin with, I agree with an earlier reply that pre-reading Europe Through The Back Door would be a really good idea. That will provide lots of information on things like Itinerary planning, money, languages and especially rail skills.
Given the occasion, try to get as much time as possible! While you won't have time to see everything that was on your list, it should be possible to get a good overview, especially since it appears you have some flexibility in your budget.
Would something like this work.
Day 1: Flight to Dublin
Day 2-4: Arrive Dublin; touring
Day 5-8: Flight to London - allow at least 4-6 hours for the trip (you'll probably be using RyanAir so be sure to PACK LIGHT); London touring - you should have time for a daytrip to either Bath or York
Day 9-11: EuroStar to Paris; Paris touring
Day 12-13: Train to Lucerne (use www.bahn.de to research your rail journeys); With travel via TGV at 300 kmH, the trip will be reasonably short; Lucerne touring
Day 14-16: Train to Munich; touring Munich. While there you could consider day trips to Fussen to see Neuschwanstein or Dachau if you're interested in history. Munich is an awesome city with lots to see!
Day 17-20: Train to northern Italy. One location that's perfect for Luna di Miele is Lago di Como and the town of Varenna. You could take a day trip to the elegant town of Bellagio or other locations on the lake. It's beautiful (that's why Clooney has a Villa there).
You could also choose Stresa or Lugano, depending on your preferences. Plan to spend your last night in Milan (or more time if you prefer). You could also base in Milan and take day trips to the lakes or Verona.
Day 21: Flight home from Milan / MXP
There are lots of ways this could be arranged, this is just one suggestion. I'd probably consider P-P tickets rather than a Railpass.
Happy travels!