I would advise
1. Learn as much as you can, including looking into the online support communities. Knowledge is power.
2. Look into low carb / grit / Bernstein approach to diabetes management. This approach often gives much more stable blood sugars. When one is not continually chasing extreme highs and lows, then the stress levels become less.
3. Do your best to treat the child the same as before, despite the diabetes (aside from the obvious of medication, testing, food management). Particularly in terms of discipline, aspirations, expectations.
4. Be practical and matter of fact.
5. Don't neglect the other children / your spouse.
6. Make the diet a family thing. If everyone eats the same, then no-one is left out.