A nice project for the kids to enjoy. They can do all this themselves, with supervision.

This is a great project for the family!

Instead of using a heap of potting mix, fill the box up with hay and put an inch of potting mix. This will help the seeds germinate due to the warmth coming from the hay. Could always
Just use a bale of hay but the box wont have birds picking it out for nests

Good idea, especially the sweet pea part. Loved growing them when I was a kid.

Great idea been wanting make a garden with kids

you could even make this wooden box yourself