Bikes make for a fantastic gift for children. They're fun, safe, and encourage the child to be active and enjoy the outdoors. The most important thing to consider when buying a bike for a child is the wheel size.
This relates to the height of the child more than the child's age, however, for simplicity this guide will refer to the suitability of the bike relative to approximate age groups. Given how quickly young children grow, it is important to speak to an experienced consultant in order to get the longest useful life out of the bike. Additionally, for safety reasons it is important that your child is riding the correct sized bike that they can safely and easily steer, brake and dismount from. Apart from size, the other important consideration is the frame. Steel frames will be heavier and more difficult to ride for beginners; and also prone to rust. Alloy frames, while more expensive, will be lighter and resistant to rust.
Kids Bikes - 12"
Suitable for kids 2 - 4 years old. These bikes come with training wheels, and may feature a push steerer so the child can be directed when required.
Kids Bikes - 16"
Suitable for kids aged 3 - 6. Generally come with training wheels and no gears. Some children may not have developed a lot of the strength required for riding, so the bike's weight will be an important consideration. For older children you may want to consider a 16" BMX for a stronger, heavier duty bike.
Kids Bikes - 20"
Suitable for kids aged 6 -10. This is also the standard size for a BMX wheel, and given the lack of gears, the kids bike and BMX hold a lot of similarities. The main difference is a kids bike will be lighter and easier to ride, and a BMX will be heavier and more durable.
Kids Bikes - 20-24" Geared
As the child becomes a more confident rider, geared bikes will become a consideration. 20" bikes are suitable for ages 6-10; 24" - ages 8 -13. For children that are quite tall, or around 13-16 years the next progression will be to an adult MTB in XS size. The MTB style is most suitable due smaller wheels, which gives lower ground clearance, as well as improved balance and stability.