If you aren't yet a subscriber to Gaslit Nation, you should consider subscribing now. Better late than never.
Check out New Eastern Europe's site for trusted organizations and charities who are in Ukraine or organizing assistance for Ukraine. Please consider supporting their efforts. Check often, the list is regularly updated.
The Guardian (UK) also has a vetted list of groups raising funds to help medics, families and children.
Some well-known, highly-rated international charities that are helping aid refugees and children: