In rec.crafts.metalworking, SteveB wrote:
I want to build a project with my 8 and 10 year old grandsons while they
spend the time with us. I want it to be one for each of them, and
something that would last. I want it to be useful, or decorative for
their room. They might only get to do some filing or bending, but
something that they could help build.

Suggestions?

Couple of months ago at a Maker Faire, I saw a quicky project to do
en masse that was building a metal tray with handle of the sort you find
in tool boxes. I think the design was whittled down to just cutting,
bending, and pop rivets, but it was a popular activity.

A full sized tool box with lid and tray would be a memorable project with
a useful result, even if it gets filled with toys and not tools.

Myself, I made an electric vehicle for my (then) 12-year old daughter.
I mashed up a free second-hand four-foot diameter "cupcake" tin with $50
as-is electric scooter (ended up only needing new charger and batteries).
The bulk of the project was making a chasis to attach the cupcake tin to
the scooter.

Electric or two-stroke engine go karts, and similar wheeled items, are a
lot of fun for that age range, and off-the-shelf devices can easily be
repurposed into more interesting creations. I've seen leaf blowers made
into small hovercraft and cordless electric drills used to power bikes.

What makes a good suggestion will vary a lot with what tools and skills
you and they have and what budget you have.

Elijah
------
is a lot more comfortable with electric than gas engines