2 weeks London & Europe??

Either way works. Obviously, your idea of London-Paris-Bruges-Amsterdam keeps the distances a little shorter than daughter's London-Paris-Germany-Prague. But a budget flight (www.skyscanner.com) can be a good choice to connect further city pairs like Paris-Berlin, and then from Berlin it's a 5-hour direct train ride to Prague. Rick’s Train Travel Time & cost Map gives you an overview of faster train travel times in hours.

Two trips. You will have a much better time and will not be rushed. I might even pare down Trip one to just 2 places as there is lots to see in England .

I travel with my dad and we have found less is more .
Have fun

Interestingly, I am planning a 2 week trip for Dad and adult son, all by train. Dad has never been to Europe but son has been to Germany and Austria. We are flying to London then going to Belgium, traveling through Germany into Switzerland and flying home from Zurich. So, I guess my answer is obviously that I don't think it's too much. Although, our trip deliberately does not include Paris, because I think 1 mega-city is enough for this trip, but that is a personal preference.

Frankfurt is quite a good place to be a tourist. There are enough sights to fill 2 full days and it's easy to day trip to Mainz and Wiesbaden. To add more variety, after London and Paris, take the train to Strasbourg and spend at least 2 full days there, add another for a day trip to Colmar. Then train to Frankfurt.

Are you the mom or daughter?

Can you do it? Yes. Should you do it? I'm afraid that is a question only you and your traveling companions can answer (which I know isn't terribly helpful!).

I think in order to answer the question, you should begin by asking everyone going what do they want to see/do in each location? What is their preferred travel style? I.e. do they like to be up and about early and "on the go" or do they prefer a more leisurely pace? The answer to those questions will help you narrow down the amount of time you'll need in each city. Once you've figured that out, add in your travel time between cities (figure 1/2 to 3/4 day per city change for checking in/out of accommodations, travel to and from train/airport, etc., etc.) and then plot out the trip. If you find you're short of time (which I always am after going through this exercise) go back and re evaluate - what is really important for you to see/do? Obviously that answer will be different for each of you and thus will require some compromises!! I recognize that this is a rather lengthy process, but I've found (after almost 30 years of travel planning for my family and others) that it's the best way for me to plan a trip that works for everyone because it forces everyone to really think about what they want out of the trip! Good luck!!!

this is what the trip looks like now:
Day 1 fly to London
2- 3 London
4 to Paris
5 Paris
6 to Bruges
7 Bruges
8 to Mainz,Germany for 1 day river cruise
9 Rhine River area
10 to Munich
11 Munich
12 to Prague
13 Prague
14 fly to Frankfort (cheapest place to leave from to get back to US I have found)
15 fly home
We could add 1 or 2 days someplace along the way if needed
Is a day Rhine River cruise really worth it? & not too many things in Paris are of interest to me so that is why only 1 1/2 days
and Munich looks better than Berlin.

If you don't care much about Paris, you can fly cheaply from London City Airport (among others) to Amsterdam. That makes your next train ride to the Rhine River much shorter and cheaper.

In my past flight research, flying out from any major city in at least western/central Europe all costs about the same, using the multi-city search function. The day that you spend getting to Frankfurt on a non-affiliated flight connection is worth something. It's 7 or 8% of your whole trip, plus at least $50 per person for the flight.

Some towns are easy enough to cover the highlights with 2 nights/ 1.5 days of sightseeing. These are generally the smaller towns, like Bruges or a portion of the Rhine. For London and Paris, I think 3 nights is the bare minimum and Prague also usually gets at least 3. All of this assumes that you're getting out early each day, to make the most of it.