Not sure about the overall route but I'm sure you'll have a wonderful time in New York. Depending on which parts you've been to before, I'm sure there will be a bunch of new places to see, so spending multiple days there seems ok to me. High Line in September is nice (but also really in any season), nearby is also Little Island which opened recently. the vessel/hudson yards is also cool and you'll get some cool pictures but you probably won't need to spend too much time there. you could also do governor's island, or explore Brooklyn. I also recently came across the gesso app's audio walking tours which I prefer because there's a lot about interesting local history.

Sounds like you'll have a great time in all these cities - hope it goes according to plan!!

Any chance you could fly to Atlanta instead of Miami? This would give you the option of taking the Amtrak Crescent route to either New Orleans or to Washington DC. If you go to New Orleans, you can spend a day or two there and take the Amtrak City of New Orleans to Memphis. The CONO goes north from Memphis overnight to Chicago. From Chicago you can go to either NYC or to Washington DC. Both are overnight trains which saves a bit on hotel charges.

Hello all! Thanks for the data!
I have an update: we changed our flights to arrive to NY instead to Miami, so this is our trip as for today:
DC 4 Days
Flight
Memphis 3 Days
Car
NoLa 4 Days
Flight
NY 10 days
Cheers!

That's a nice itinerary and time spent in each place I think.

Have you been to Charleston ever? That is a worthy choice for a trip also. If you didn't want to spend 10 days in NYC you could pretty easily include it.

Welcome, federicofalasca3652. Expect you have done a "What to Do In..." search for the various cities on your itinerary. If not, at least do Washington D.C. It has a wealth of interesting venues. There are more than 15 Smithsonian museums so do Google them to get an idea of what meshes with your family's interests. You might need more time there.