Our DD built one a year or so ago. We have 3 very active kids (and their friends) who play with them frequently - the pieces can be taken apart very easily, but don't break easily. There is one part with a little door and the 3 gems inside - the door on ours has broken when someone tried to close it with the gems in the wrong spots.
It's a large/heavy lightsaber, IMO, the smaller lighter Mickey lightsaber is much better for the 5 and under ages - for size reasons only - but if your son is older, then the build your own is great.