thanks for the great feedback guys, I will think and replan accordingly.
might do the day trip to bruges and spend two nights in brussels

I agree with the staying in one place and not rushing it our original plan years ago was when the kids got older to just visit one city every year and spend a few weeks there, put the kids in a language school and absorb a different environment.

my kid is named after the city of siena otherwise we would probably skip Italy all together since we have been there before.

the downside of this trip is for us parents are visiting cities, we have already been to (except Belgium), and wanted to throw something different in there.

per your advice,I think we may skip Barcelona and do rome since its much closer.

revised itinerary looks like

London 4 nights
brussels 2 nights (day trip to bruges/westvletern)
paris 4 nights
venice 3 nights
Florence 3 nights (day trip to sienna)
rome 4 nights

and also considering doing this trip in reverse, so flying to rome the day we land in London, so travel day back is not a beast.

thanks again for all the advice.