Mongoose FS1 Restoration – Worth it?

Essentially my old bike from the 80's (stored in a dry attic for the past 40 years) that I'm debating whether to restore or not.

Photos can be seen here.

Unfortunately it looks like the seat tube has broken off just below where the clamp would sit (see other FS1 photos for comparison). I'm not even sure if this is possible to repair and what the cost might be?

At some point it was deemed a good idea to touch up the paintwork but as you can see it was a bad job done with a darker green. Given the decals aren't in great condition either would it be sacrilege to have the bike stripped down and re-sprayed / powder-coated in it's original green (or close match) and new FS1 decals applied as a first step? 

Other than this do you deem the current condition worthy of a restoration? Ultimately i'd want it for my 7 year old son to ride so it doesn't need to be museum perfect, but I'd still like it to look relatively clean / new. 

I'd have to source some Skyway mags for it and a set of new handle bars (I don't have the original mongoose bars anymore) plus some other bits obviously. 

Worth it??