When I first meet a child for therapy, I always ask parents to tell me what their child likes to do. What characters, what toys, what games, what videos, what books.... So many times parents of children with severe speech and physical impairment look at me like I'm a little crazy when I ask about board games. "Well, she would probably like them but she can't do it." Since that sounds like a challenge, I have been adapting board games for many years. (Plus, I like games and my own kids are getting too old to play Candyland with me anymore!)
The first step is to make sure your child has a means to communicate general control messages within the game: gestures/hand signs, communication device pages specific to the game ("my turn," "you go," "draw a card," "go fish," "oh no..." or core words to say "go," "me," "like," "I," "you," "want," "turn..."
The next step is to make sure the child has some way to indicate their choices specific to the game. For games that include color or number choices, that's a usually simply a matter of using their communication device to indicate a choice. If your game has very specific choices, like this Shrek Memory Game...
I put velcro dots (soft side) onto each square of Candyland and, velcro dots (hard side) onto the bottom of the little playing pieces. This allows children who can move the pieces, a target and a little sticky support to keep their pieces on the correct square. For my friend Gwendolyn and her family, this little trick means that her Mom can hold the board up as close as necessary to help this sharp little girl with cortical visual impairment see the pieces better.
The final step is to forego any self-dignity and get into it! You can make a paperclip exciting if you are enthusiastic enough. When you expect your child to be able to participate fully and to have FUN, they will gain the confidence to jump in and play. Remember, they probably think they can't do it either, since no one ever helped them try. The long and short of it is to assume that there is SOME way for all children to participate in a board game. Usually, it's really all about communication. Sometimes it's about physical access but, if you can't figure out the physical access then, it's really all about communication to tell people what you want your game pieces to do! Which, of course you know, we really like anyway! :)