We are planning to travel with 10 year old to Madrid on Oct 6th and fly out of Paris on Oct 15th. Would like ideas on places to visit and things to do.
Not very architecture heavy - a few highlights will be good. A few on the wish list are Barcelona, Malaga, ROme, Florence. Not all listed places but one of 2.

Welcome to Fodors. We moved your topic to the Europe Forum

You are departing on the 15th. Are you arriving on the 6th? Allowing one day of travel from Spain to Paris, leaves only 7 full days for sightseeing and other travel during trip. Are you planning on trains, planes?
There are fast trains from Madrid to Barcelona (about two hours) and also from Barcelona to Paris (don’t know the time).

I would probably just do three days Madrid (include day trip to Segovia), fly to Paris, four days Paris.

However, though rushed, you could
6th arrive Madrid
7, 8 Madrid
9, train to Barcelona, afternoon Barcelona
10, Barcelona
11, train to Paris
12, 13, 14, Paris
15, depart Paris

If your flights are not set in stone, consider changing to a combo of London and Paris. Easy and kids love London.

Yes, agree that it would be nuts to try to cram Italy into your allotted time. We did Madrid-BCN (train)-Paris (flight) in 15 days and it was OK. You essentially have eight days for your travels - arrive 7th, depart 15th. Even Madrid, Barcelona and Paris will be cramming a bit. Train Madrid to BCN takes 2.5 to 3 hours. High speed train from BCN to Paris is over six hours, so that's basically a day shot. Flying BCN to Paris takes a bit under two hours, would be much better to fly if you must do Barcelona. But I'd recommend you do just Madrid and Paris, flying between the two (Madrid to Paris by train is a very long ride, at least 15 hours or more.)

Aside from architecture not a first choice, what DO you wish to do/see?

Options for Madrid to Paris by train: https://www.seat61.com/international...tm#Spain-Paris

Info on Barcelona to Paris by night train (note that this requires a change at Cerebère or Latour de Carol: https://www.seat61.com/trains-and-ro...eper-train.htm

I agree with the others here - you have far too little time to cram Italy into this and ideally you should concentrate on Madrid and Paris especially with a child in tow which will make everything slower and more complicated.

You must drop Italy on such a short trip. Even Barcelona and Malaga are not between Madrid and Paris.

well, Barcelona kind of is. Certainly if you take trains, although not as the crow flies. I could see doing what Sassafras suggests although I would add another day in Barcelona and one less day in Paris probably. Because then you'd have about 2.5 days in each city. Plus the train to Paris from Barcelona is about 7 hrs, I think. So if you leave Barcelona on the 8ish am train, you get into Paris around 3:15 pm. So still can do something that evening.

I wouldn't personally do that but you could. I'd just stay in Spain, plenty to see there, then you could visit Madrid, Seville or Malaga and Barcelona. Logistically, would make most send to fly into BCN probably, and fly out of Malaga or something. It depends on flight ease. Where I live, you can't fly nonstop to/from any Spanish major city, so you'd always have some connection time going home no matter what. But I have flown to/from both Malaga and SVQ from elsewhere in Europe (and Madrid probably) and there are plenty of flights from Malaga. Easyjet flies from Malaga or Barcelona to several places in the UK and to Paris. It does fly to/from SVQ and LGW, also.