Our well-traveled family of mom, dad, and three teens is planning to visit family in Heidelberg for a couple of days, then fit in a jaunt to Paris and Amsterdam. We have 10 days and will be flying out of and back into Seattle. We plan to fly to Frankfurt, and depart from Amsterdam. Is this a doable itinerary? Thoughts of whether to train between cities or take a flight? How to maximize time in Paris and Amsterdam with just a couple days? Thanks in advance!

How long do you plan to spend in Heidelberg? Or is that yet to be determined? I think 3 cities in 10 days is OK but ambitious when two of the cities are biggies like Paris and Amsterdam. Heidelberg will not take you very long, but of course you will have jet lag (most of one day lost), and you will want to catch up with family also say another day. So say the first 3 days were spent in Heidelberg, just for argument's sake. Train will stop you backtracking to Frankfurt, but there's another half-day lost. So say a night in Paris. Then another 2 days in Paris, not much but enough to scrape the surface. Then another train to Amsterdam (another half-day lost). So in total this might look like:

Day 1: land in Frankfurt, train to Heidelberg, jetlag. Night in Heidelberg.
Day 2: see Heidelberg and hang out with family. Night in Heidelberg.
Day 3: see Heidelberg and surrounds (for example, perhaps Hirschhorn). Night in Heidelberg.
Day 4: Train to Paris: Get bearings in new neighbourhood. Night in Paris.
Day 5: Sightsee in Paris. Night in Paris.
Day 6: Sightsee in Paris. Night in Paris.
Day 7: Train to Amsterdam. Get bearings in new neighbourhood (maybe a canal boat). Night in Amsterdam.
Day 8: Sightsee in Amsterdam. Night in Amsterdam.
Day 9: Sightsee in Amsterdam. Night in Amsterdam.
Day 10: Pack up; last sightseeing if time (perhaps a run to a supermarket to stock up on goodies? ) Flight home from Amsterdam.

If your ten days is not 10 days on the ground you would have to rework this a bit. You gain little by flying as you still lose time in airports. You actually don't have much time on the ground in Paris so maybe rework the Heidelberg section to give yourself another day there, if the family thing is less important for you (up to you, I think actually sightseeing with family would be nice). If this works for you you can start filling in some of the details.

Lavandula

I think lavandula has given you some excellent ideas. I also agree that your plan is ambitious -- I would say exceedingly so. You might consider skipping Amsterdam -- there's more than enough to keep one busy in and around Paris. Or skip Paris and add time for other parts of the Low Countries.

When are you planning on taking this trip? Have flights already been booked?

Please don't fly, consider a train between cities. It is approximately 3.5 hours to train from Heidelberg to Paris, but check the DB website to confirm https://int.bahn.de/en/ (I admit I did just a quick look of transit times). Train from Paris to Amsterdam as well. Check out Rome2rio for more info, but verify underlying links https://www.rome2rio.com/ Another great resource is seat61.com for all things train and public transport.

Does your 10 days include your flights to/from Seattle, your time with family in Heidelberg AND Paris & Amsterdam? If so, in my opinion, it would be too much. While Heidelberg, as already mentioned, really only takes a couple of days to cover, if you are wanting to visit with family, I'd probably want longer. YMMV

You say you are well-traveled, have you been to Paris and Amsterdam before?

To maximize your time, assuming you have not been, plan ahead on your sightseeing. Many landmarks and attractions in both Amsterdam and Paris either require or recommend advance booking. With your tight itinerary, you do not have time to stand in line at say, the Anne Frank House, the Louvre, or Eiffel Tower, etc. etc. if these places are of interest. And keep in mind, timing. There is a big difference in time at an attraction to seeing it on the outside vs. going up/in/on one. Eiffel Tower itself only takes a few minutes to view. But if you want to go to the top, you need to plan your schedule around that and the tickets for it.

What a great chance to see family. But just for a couple of days?

Certainly use the train to get around, flying will be slower and more damaging.

From my point of view I'd cut one of the biggies and I'd try to fly back from one

Now, when are you coming, what are you interested in and are any staying on any longer than this very very short trip?

Welcome to Fodors. Is it 10 total days home to home . . . or 10 days on the ground in Europe meaning 12 day total??

If the former -- then you will really only have 7.5 days free for seeing / doing. Then you use ½ to one full day moving from one city to another. Which IMO means you have enough time for Heidelberg and either Paris or Amsterdam, not all three. Especially with a group of five so that everything will take longer.