If you have more than one small child or you have just the one toddler but you want to take some stuff along with you all on a bike, a bike trailer is a grand tool for the job. They connect on the rear quick release of your bike via a hitch. You can quickly remove the trailer at any time (the hitch anchor stays discreetly on your bike). Most trailer fold down a bit for better storage and portability (holidays and so on). The more you spend the less weight and more features you will get.