i can only speak from experience, my 4 yr old son wanted a boat 'cos dad has one ( well actually several ! )
i thought about the ready to run option for him , something he could basically slip the lid on , stick the stickers on and get wet and get running, after all he is only 4....
but imagine my surprise when in the local modelshop ( sadly now clsed !) when he started picking at styrene sheets and telling me he also needed some wood for his boat...... and he then started to look at the more unusual extruded sections of plastruct.... he had no idea what he was going to make but he wanted these materials.....i nearly steered him away from these bits and bobs and then the penny dropped.... he wanted to 'create' and not just 'buiLd'-
i was sure something brightly coloured , sporty looking with aerofiols and fins on would be what he would go for in the shop- you know the stuff that frequents the windows of most hobby shops and some trade stands at shows, ... the stuff made in their thousands in the land of the rising sun.....
after a minute or two i decided not to dampen his idea, we bought several types of material, and glues, and paints and took it all home, we then purchased a GRP hull on line about a week later, not of anything in particular but one he liked the look of !- he then sketched ( well more of a well meaning scribble) an idea of what he wanted to build, and then he started to mark out on the materials what he planned to make, carefully the boat began to take shape,
but his enthusiasm to build, and to solve the problems as he went along was worth every penny- that to me was the most worthwhile bit , ok , what he actually put together is just a 3d version of what he had in his head, its a slow plodder of a boat, its a twin screw vessel, very boxy type superstructure,pretty ugly in fact, looks a bit like a house boat !!! but he loves it.... and hopefully the true model boater in him has been let loose, and as he gets older he may build something else, but the pride he takes over his boat in unreal,at shows he tells everyone ' i made this'
a ready to run boat would have been alot quicker to build but i bet by now it would be in the bottom of the wardrobe in its polystyrene box..... he however has his boat pride of place on show in his bedroom....
so whatever you decide lets not tar everyone with the same brush, not all youngsters want to sit and play xbox, or playstation, not all want to operate model boats..... not everyone can or wants to scratch build, thats fine, whatever we do lets agree on one thing -and that is model boating in whatever form it takes is a rewarding pastime, and hopefully long may it continue !- at least now my son knows how to mix araldite and how to carefully score and snap plasticard... valuable skills in later life !