We have a bus that our kids will be riding in frequently...think school bus seats with lap belt only. What is the safest way to ride? My kids are 6, 5, and 2. I think the oldest 2 might be ok in just the seat belts and I can use a convertible for the two year old (scenera?). He must be restrained because I do t want him sliding around or trying to run around. But what is the safest way to transport them? I've used a car seat on a charter bus before, but this is a personal vehicle.