Wouter,

A balance between performance and ease of building needs to be struck. Your concept is better in some ways but it will take longer to build.
To keep this real cheap it may need to become a club project with a production line type setup. If that is the case it may be better for a less optimal design that is much quicker to build.
If dads were building for their kids in a home environment the pressure on time may not be as great.

I'll detail the steps as I see them with guesstimate times.

I'll leave the rest up to you.

Please note the times below are just a guess.
You never know until you give it a go.

You only mark out one panel and it is used to cut all others with a router.
Glue and screw on stringers and gunwale, make the keelson and the sides are glued and screwed on. Wire up bow. Glue in props between the stringers and fillet inside of bow all in one operation. Laminate ply to underside of foam for deck. Leave overnight for resin to cure.
Maybe 10 hours

Remove screws, fill holes and waterproof inside and outside of hull and under deck. Fit beam landings. glue on deck . Leave overnight.

Maybe 4 hours.

Shape and glass deck. Glass outside of bow and along keel. Leave overnight.
Maybe 4 hours.

Paint.
Depends on the finish you want.