Good morning, I would like to help you today.
I can relate directly with your concern, and would like to help you. I myself have 19 month old twins, who as well are a bit behind their peers in regards XXXXX XXXXX I agree that children (people) are individuals, and each one of us develops at our own pace. An example is my brother; when he was 2 years old, he could say very few words; now at the age of 25, he does public speaking, and you can't keep the man quite, and he did not attend speech therapy. This however is his story, and may not be the same for all children with early speech delay. I would recommend you looking into a therapist who specializes with speech in young children. At least by getting a professional opinion and evaluation, you will have a better insight to what can be done to help your grandson. I have as well enrolled my twins in an early head start program to aid their development, as I think that although the pace that they are developing may be their own; it's better to be safe than sorry.
This article provides an idea of where you should expect your child to be in his speech development: http://kidshealth.org/parent/emotions/behavior/not_talk.html#
You are doing well with continuing to talk to him, read to him, label things around the house with words, and point things out and name them regularly. Encourage his language development with educational programming as opposed to cartoons. Here's a link with a few online games and activities that are good for helping children learn speech: http://www.talkingchild.com/games.aspx#games2
Here as well is a PBS development tracker for children ages 2-3; there are also a lot of useful links on the top of this page:http://www.pbs.org/parents/childdevelopmenttracker/two/language.html
Please let me know if you need any further ideas or resources; I will be happy to help.