Eric
Best of luck with your project.
There are various plans available for good model Spitfires.......probably the most accurate is by Brian Taylor at 83" wingspan (A Mk.VIII IIRC). These plans are available via Traplet Publications. Enlarging these plans is not an issue. You need to have them digitally scanned then enlarged to your desired scale before re-printing. DO NOT simply have them photo copied & enlarged.......'roller' type photo copiers suitable for copying large drawings such as these are well know to stretch/distort plans rendering them inaccurate.
Another excellent source of Spitfire information is Monforton Press. They offer a fantastic book and set of scale drawings of the original (not a model) Spitfire.......
http://www.monfortonpress.com/.....I used these drawings heavily on a 1/4 scale project a few years ago.
Timber selection......if this has to carry a small child, formers, ribs & skinning would be predominantly birch plywood with spars & longerons from pine (or similar). Saying that......being the proud owner of a 6 1/2 yr old son (almost 1.2m tall), there is no way he'd fit in the cockpit of a 33% Spit.......if this is your requirement, you'll be looking closer to 50% scale I'd have thought.
Tools......sounds like what you have should be fine (as long as it includes a medium size bandsaw & a decent disc sander)
Time scale.......this really depends on the level of detail & functionality you want to include, the the 1/4 scale version pictured below was around 1800 hours start to finish. (these things always take a lot longer than you may originally think)
Hope this helps.....
Phil