It's really cute!
I'd change up the UX a bit.
1 - For the drag and drop, I'd keep the original letter in place, and just make the original slightly transparent as you drag. Reason being, as you drag on a phone you can't see the original letter since your finger is on it... so leaving the original as an indicator is good.
https://master--5fc05e08a4a65d0021ae0bf2.chromatic.com/?path...
2 - For the drag and drop, I would add a a "drop indicator" as you mouse over each square.
https://master--5fc05e08a4a65d0021ae0bf2.chromatic.com/?path...
3 - For things like "Triple Letter" I would change it up... "x3" -- I know you're going for "Scrabble" but frankly the text is a bit small for older people, who I think make up the "Dads" in your audience.
4 - Instead of "Delete" I would change the word to "Recall" for recalling letters you placed on the board.
5 - For the Colors I would go more vibrant.
6 - For font sizes, bigger is better. https://imgur.com/a/kduZzwl
7 - For buttons, I would suggest having different colors for different buttons. Having them all black means you have to read through them all... having one as a clear "primary" color helps.