We have a longtail cargo bike, with a child carrying set up. The kids sit on an extended rear deck, with a cushion on top surrounded by a hoop-tie bar setup to hold on to and contain them. We love it, it carries all 3 of our kids (1, 3, 6) in a pinch, but 2 comfortably including any gear or groceries. It has the ability to tow our older daughters bike, so she can ride when it's calm, and catch a ride if the roads are too busy or if she kids tired. This makes it a perfect go between for those years when your kids aren't old enough to bike far on their own, but are too big to comfortably ride in trailer for long. It has a 20" rear wheel, which lowers the center of gravity making it less tippy than some other setups. Cargo bikes are fairly pricey new, but they appear to hold their value well - but I don't think we will sell it soon, it's fabulous for groceries for our family of five!