That is rad. All kids should start to learn asl as young as possible. My grandkids are learning. My grandson is less than a year old and he knows signs for milk and toilet and about five others. My other two granddaughter, ages 6 and nine know most of ASL 111 from the book. They know their colors and lots of stuff, and they can do the alphabet and sign names etc. They are also way ahead of their classes now in reading, writing, and spelling because they were taught in conjunction with ASL. Kids can learn to sign about three months earlier than they can learn to speak. So, do look into it. You can go to Lifeprint. on Web, or ASL University or ASL pro. They are all free Web sites and have video signing, especially for the simple signs.
When we started teaching our grandkids, we just showed them the sign with the thing, just like you do with english, but we separated it. We didn't say the words, but showed the sign. Like hand them milk, and then use the sign. I think they learn faster that way. Anyway. I am hearing, and I am sure that I don't have all of the info. But, I wanted to encourage you to teach your kids sign when they come. Geez, I talk too much.!