Depends on where you live. Even with kids, you don't need a car in London. You can rent cars over the weekends. Hauling groceries is a PITA but with a good backpack, this is also solved. If you live in some place like Barbican, everything is around your doorstep, so no need to haul groceries. The downside - you pay higher rents. Outdoor activities - you can rent over the weekends unless you are kayaking, skiing or climbing and don't want to haul gear in and out of your car every time you reach home.