If a child is having trouble writing clearly, you might consider a consultation with an occupational therapist or check with the child’s teacher to see what programs have been tried. Some programs like Handwriting Without Tears is readily available.
If, however, a child is having trouble with formulating thoughts to write, you might reading together and [...]

Probably not. Research (Berninger, 2009) demonstrated that children in the sixth grade and below compose faster with a pen than by any other method of transcription, including keyboarding. This was true of children with and without learning disabilities. You can read the study in the journal Learning Disabilities Quarterly, 32 (3).

We collect a sample of the child’s writing (without assistance) and administer tests (like the Writing Process Test and other language tests for vocabulary and spelling) to obtain a complete profile of your child’s language level and use. We compare where your child’s writing skills fall against the grade level standards (published by the state) [...]