Now is a time when the kids can start to become biliningual by learning American Sign Language. I have included a couple of charts and some resurces to get you started. The Alphabet is only one way to start, for kids it may be easy to to just start with a few basic words or phrases.American Sign Language (ASL) was first recognized as a language in 1965, it is not an international form of communication. There is no international sign language. In fact those who sign may do so not only in a vareity of languages but it includes local dialects. A person in Boston may not sign the same as someone in Texas.
The Deaf Community is an entire culture and there are many things to understand. I am no expert. So please do some rearch and reading, you and your children will be better with any new found tools. One simple place to start is with the National Institute of Health https://www.nidcd.nih.gov/health/american-sign-language where they maintain a list of organizations and resources. A great way for kids to learn is by seeing other kids sign. One You Tube channel, Laura Berg Life aka Smart Hands http://bit.ly/1OT2HiC , has videos with just that, kids signing to teach kids.
How ever you get started, do start.