Hard to give you advice since we agree with everything you say. In places like Rome, my DW and I will spend all day walking miles around the city. IMHO there is no better way to see any city than on your feet. But your kids cannot do that kind of walking so I guess you will need to compromise. Whether you feel comfortable dragging your children on and off public transit...only you can decide! When our daughter was young and we dragged her to Europe (we took her through 4 countries on a Eurorail pass when she was 9) we found that frequent ice cream (gelato) stops and Orangina (she loved that drink) went a long way to solving the child issues. But, not sure this will work with children as young as yours. We started our daughter on cruises when she was 5 (the old Fairwind) and more than 20 years later she still fondly remembers that cruise. But, taking children that age through the streets is different and sure does present logistical problems. Also keep in mind that in the summer, it can get quite hot and humid in Rome and some other Med cities and this can create addtional misery problems for children and adults. You will need to keep your flexibility, patience and sense of humor and hope that your children turn out to be great travelers.