Did you ever get a toy or a craft that you had your kids try and they enjoyed for a bit then you once you put away, well out of sight out of mind. Then we fast forward a couple of years and a second child finds them and well you get this!
I got this container of PYSSLA from IKEA or perler beads as I've heard they are called in our neck of the woods. There is a 4 piece shape discs you use to place and shape with beads. This craft has kept my boys busy for hours. It isn't very expense at $8.99 for jar and $2.99 for discs. Michael's craft store also has an array of perler bead kits if IKEA isn't accessible to you or you can shop online at Amazon or the like.
My older son likes create his own designs after trying a few off the internet. Here he's trying to make a Mickey Mouse head. Once they are done creating their design you then take some parchment paper and iron carefully not to melt shape disc (as I've done slightly in past).
It's a great activity to take them away from electronics too for a bit. They are small and tricky to hold and place. It takes a bit of dexterity. My 4 year old loves it though and is able to follow some patterns.
With some of the trickier patterns like Disney's Dory I would help by doing the outer design and let him fill spots. I actually find it enjoyable too working with him, kind of like you can get into colouring, hence the craze of adult colouring books.
If you are looking for ideas on what to make check out my Pinterest board Perler designs for some inspiration.