What does Chris' mother mean when she tells Chris that his dad is "chewing up his words to see how they taste before he lets them out"? (Paragraph 7) on dreams need a push

It means that his dad was not quite sure about Chris joining the wheelchair basketball team.

Explanation:

When Chris met with the accident, his dad Jim took the blame to himself and was never over it. His dad was a man of few words and kept almost everything to himself. When Chris told about his parents about the wheelchair basketball team, his mother approved it instantly but his father just stared at him and mumbled few words. At this, Chris' mom tells him that his dad is "chewing up his words to see how they taste before he lets them out". She said it to mean that his dad was not quite sure about Chris joining the wheelchair basketball team.