Airfix are still great. Me and my 8 year-old lad have done a few (Spitfire, Hurricane, Messershmit and WIP a Sunderland flying boat), my daughter also did a Ford Focus rally car. Good honest interactive fun with the kids and not a TV/Monitor screen in sight.
Revell also do a range of high quality snap-together kits which are brilliant for kids, not only aircraft and stuff but Star-Wars as well, no glue, lots of colour and detail. Keeps 'em amused for hours!