Many families do this. The benefits of signing with a child who is pre-verbal are pretty easy to understand. After all, how wonderful is it to know what your baby is thinking before they can speak? But did you also know that the benefits of signing with a child go well beyond the baby years?
When a child first begins to speak, their own use of sign may naturally slow down for a bit, but that doesn't mean it is time to stop! A toddler who is newly verbal will likely continue to use signs as needed. In addition, the ongoing use of sign language with children has been shown to enhance both spoken language and literacy development over the years, increasing both spoken vocabulary and reading ability in statistically significant ways.
The benefits of sign language in literacy and language development holds true for not only typically developing children, but for children for whom English is not the first language, and for children with special needs.
Sign language can serve as a wonderful bridge between two spoken languages, where English is spoken in the daycare or school, and a native language is spoken at home. Because sign language is naturally iconic (many signs kind of look like the concept they represent), a child may be able to clearly express the same concept in either environment using a few signs.
Children with special needs, who may have cognitive, motor, or language delays, also thrive with sign language. For some children, their receptive language (what they understand) outpaces their expressive language (what they can communicate with words). Because sign language can tap into a variety or modalities (visual, auditory, kinesthetic), children of all abilities are often able to harness the communication powers of simple signs, empowering them to express needs, wants, thoughts, and emotions, in a way they may not have previously been able to do.
Quite simply, sign language with children of all ages has shown to have a wide range of benefits for all ages, stages, and abilities.