Itinerary Help/Critique - 3 Weeks

Is it necessary to go to Bruges if we're going to see other old cities, like Heidelberg?

No, in fact it is a bit of an outlier on your itinerary.
Rather than Mainz, use one of the smaller Rhine towns as your base, Bacharach is a popular choice, especially if you like cute old towns. Its a good base to take Rhine cruises as all the KD boats call there.

I would prefer to travel the paths of least resistance, and reverse the order of the cities. I love Amsterdam, and have driven up the Rhine River three times and visited the Black Forest twice. I prefer to spend my time in The Alps rather than going up a quiet river.

Have you considered flying into London and first visiting the U.K.?
Then take the Eurostar down to Paris and visiting your desired travel sights.
The trains are quick and efficient from Paris to Brussels/Bruge--if you've got to go there. I'd skip it.
Trains from Belgium to Amsterdam are frequent, and it's not far.
From Amsterdam, you can take trains up the Rhine River, and I suggest stopping at Cologne. You could also spend a night at Bacharach. (Read about the region on Bavaria Ben's website.)
You can be at the Frankfurt Airport in under an hour from Bacharach, and I'd suggest flying Frankfurt-Dublin on Aer Lingus.
Then fly Dublin to Iceland on your way home.

That sure is a bunch of stops. At least you're staying pretty far north where it won't be nearly as hot as the Mediterranean region.

Norwegian Air Shuttle's now flying out of Orlando and Ft. Lauderdale very inexpensively to destinations in Northern Europe and beyond. They're such a great option for travel to Europe. We're flying Orlando-Copenhagen and Bergen-Orlando for $757 in 2 weeks--great fares.

Sam, thanks for telling me what I was feeling in my gut - I think we'll dump Bruges. That will give us an extra day on our Eurail Pass, if that's the way we go. I'm still crunching numbers between the pass and point-to-point tickets.

David, thanks for your suggestions. I've checked almost every possible permutation of plane ticket purchases with various starting and ending points. So far, the best deals I've found were Icelandair for the first leg from Orlando to Amsterdam with a layover in Iceland, and a return flight from Dublin to Orlando using Aer Lingus. I'm going to keep looking, though, and the "direction" that we actually travel in will depend on that. We're skipping the Alps this time because we spent a LOT of time there on our last trip, and I'd really like to see the Rhine.

You could also do Iceland Air to Frankfurt (3.5 hours), do day trips to Heidelberg, Mainz and the Rhine from Frankfurt. Fast train from Frankfurt to Amsterdam, then train to Paris, train to London, then Dublin. This might be a bit more of a logical progression for you.

Hi,

There is an early ICE train Frankfurt to Amsterdam direct. In 2013 I did that as a day trip, r/t, used a day on the Austria-Germany rail pass to/fro Frankfurt to Duisburg, booked a discount ticket for the Duisburg to Amsterdam segment of the ride, ie, left Frankfurt early and returned that night.

I think your itinerary looked perfect before. If you travel down to Bruges there's some amazing things to do and see between Amsterdam and there:

See the Delta works, the giant storm doors at Rotterdam, The Waternoodmuseum about the 1953 flood, Aalsmeer Flower Auction, and the Arnham folk museum.

After or near Bruges there's Ypres, where "In Flanders Fields" was written and you can see some of the trenches that they've preserved.

Plus Netherlands and Belgium are fun to go around on bicycles.

I think your original plan was pretty much perfect given your time and 'wishlist'.

Rather than dump Bruges, you could reduce it to perhaps a one night stay.
Travel very early on Day 7 to get you in Bruges before midday. Travel time is 2hr 46min for Amsterdam to Bruges.
Then travel on to Aachen or Cologne very late on Day 8. Travel time is 3hr 07min for Bruges to Cologne