Sand writing is a lovely tactile way to learn letter shapes… but sparkle writing is something that is hard not to be excited about starting!
Simply fill a container with glitter (not too thick, you only need a couple of mm deep for the letters to form).
When they want a fresh surface to write on simply shake the container slightly and it will clear the way for more creations.
The 5yo wanted to write words, the 3yo was happy making letters and shapes (all these activities can be supported by showing an example for them to model their own work on)… but by far the most fun was had when the 3yo returned to play on her own; she was consumed for quite some time drawing little pictures by herself. It served not only as a shape recognition and letter forming practice, but also as a quite, meditative time for the kids throughout their day. Quite reflective time (forgive the pun) is essential for processing information, particularly for those with more introvert tendencies, and is as important to learning as the abundance of information and stimulation that we must also provide to their developing minds.
House tip: We welcome glitter in our world, but I know many sensible people who avoid it because of the excessive cleaning up required after the fact. To my surprise this unmonitored glitter quite area did not spread (like other glitter art experiences do!) and even more astounding was that it lasted an entire week without mess. I believe the heavy container that we put the glitter in helped with this, and because it was seen as something special the kids were happy playing with the magic dust in their own time, and without spreading it!