Hello,
Our first son has chronic kidney disease and is awaiting a kidney transplant. Due to his condition, he suffers a severe developmental delay in speech. We were told he will catch up once he is transplanted, but his inability to communicate his needs was proving to be very frustrating for him. He is 2.5 now.
I decided to try signing and started with the baby einstein DVD: My first signs. It was good, in that it introduced my son to signs and he did begin signing ball, daddy and sleep rather rapidly. But beyond that, it is pretty lacking.
He is now seeing a speech pathologist and she recommended the "Signing Times" series. It is a comprehensive series of DVD's from a TV series that used to be on PBS. What is great about these DVD's is that the mother/children on the DVD actually use ASL (american sign language) because her daughter is deaf.
I don't know how you feel about your children watching DVD's, but honestly, if you actively watch it with them and engage them in the signs, repeating the words and the signs as the show is doing them, it works wonders.
I am also one of the busiest people I know. With my son's severe health issues and the fact that we have a 1 year old, and both work from home, I don't have the time to read books. I don't have the time to attend classes on baby sign.
Since we began signing with Max, I've found that his speech is developing far more rapidly. Lately, I hear 3-4 new words a week AND sometimes while I am working with him on a sign over and over again, he will begin speaking it before he ever signs it. This was most recently true with "More". I have also found tht he has now started using his vocabulary functionally, rather than just saying words here and there in no context.
I like that Signing Times is ASL, and I feel as if I am helping my child to speak, as well as teaching him a valuable second language. We are doing this with our 1 year old, too.
The series is available at Amazon,com and there are something like 12 or 13 in the first season and there is a second season, as well. Right now, we have episodes 1-5 and are finding that is meeting our needs right now.
The only other advice I can give you is to sign and say the words religiously. Do this over and over again. Even if you don't use a video or a class, you can still teach them sign and they WILL pick it up if you just commit to working with them on this whenever you are talking to them or to someone else in their presence.
Good luck!