Shouldn't we wait?

...and let children make their own decisions when they are older?

Some do wait. However, baptism is not a matter of imposing our views on our children, but ensuring they have a good environment for making those decisions at a later time. From birth, we make choices for our children – we give them food and clothing and a good home. What better than to provide a healthy spiritual environment, in which they are nourished with God’s goodness until they are old enough to step out on their own.