On top of that, they're just riding, not pedaling. Because carriers sit so high, they throw off your center of gravity. Ride cautiously until you get used to how the bike handles. Another option for older kids is a bolt-on tandem that lets your child hold handlebars and pedal while you provide steering, power and balance. These can be good precursors to a child's first bicycle.
Most cyclists fondly remember their very first bike.
Learning to ride a bike offers a sense of accomplishment and freedom. Your child has a lot of growing to do, so don't break the bank on her first bike. Just make sure it's well constructed, with a solid coaster brake and a comfortable seat. Do, however, make sure it fits. Also, don't forget the helmet.