My suggestion is that you forget about writing for a couple of years. There is a big difference between the muscle control needed to hit keys on a computer keyboard and the control needed to print and write. If you push too hard at trying to get them to write at this time, when they don’t have the level of either muscle control or interest to master writing, you may create resistance to new learning. To help them gain muscle control, let them color with crayons (on a plain sheet of paper, not in a coloring book) and play with small manipulative toys like blocks and puzzles. And don’t let them sit too long at that computer!
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.