Simon and Samantha Weaver, parents of Kyle, say the donation means his operation at the St Louis Children's Hospital in Missouri will now go ahead on 21st May.
A team led by renowned surgeon Dr TS Park will cut Kyle's spinal cord and re-attach it to his legs to improve his mobility in a procedure called selective dorsal rhizotomy.
We are shocked, astounded and amazed at the Williams' generosity. We can really get going with the surgery now.
But we have mixed emotions. They have helped us and I wish we could help them, but there's nothing we can do.
This huge donation will make a huge difference to us.
More top news
A fine and bright start to the week, with any lingering rain clearing away as we move throughout the afternoon.
A wet and windy night to come, with rain turning heavier overnight. Feeling particularly blustery in coastal areas.
In today's Newsweek Wales, Carl talks to Dr David Bailey from The BMA about how to ease the pressure on the Welsh NHS.