If your goal is to get your child writing, the method of getting ideas written is of little consequence. Typing, handwriting, and scribing are three ways your child can get their thoughts on the page.
If your child is planning any post-secondary education, they'll have to submit typewritten assignments. Typing.com has a free typing program that is worth checking out. However, if your child is starting to learn to type, they may not include all of their ideas in their compositions because it takes them a long time to type them out.
One way to get them to capture all their ideas is to have them to handwrite the first draft. When they've got their first draft done, they can type it out without worrying about losing their ideas.
While some students find it easier or faster to get their thoughts out using pen and paper, other students struggle to hold a pen or form letters correctly. If your child struggles to physically write, help them learn handwriting skills so they can confidently fill out paper forms. However, when they are trying to capture their ideas, either scribe for them, or let them type.
Scribing is when you do the physical writing, and your child provides the content. This is not cheating. The purpose of writing is to capture your child's ideas. Scribing removes the barrier of getting ideas on a page and affirms the value of your child's ideas.
The scribing phase may happen for a few weeks or a few years. During non-writing times, encourage your child to learn to type. Eventually, they'll be able to record their own words.
Whatever method your child uses to get their ideas on the page, make it a habit. They'll become better at putting their thoughts together, and writing time will be less stressful as you adapt the method to their current needs.