Try [url]https://eaSudoku.com[/url]! It provides a new way to play sudoku.
No timer, no need to note, no direct answer for any cell, no undo... but does have pretty good tools for you to solve any puzzles, including those 17-clue puzzles.
It's also friendly to players at any age (probably 4+). Kids may start from 4x4 puzzles and then 6x6 and eventually learn how to play 9x9 puzzles.