Can't recommend XM T5000 Offshore suits highly enough. Quality kit. Fleece-lined collar, hi-trousers, reinforced (Cordura) on elbows and knees, reflective piping and strips, storm pockets, loops for life-jacket, fluorescent hood, breathable and waterproof. Comes in sizes (S) to (XXL), red or gold, for £150. See marinestore.co.uk
You can always sell on, or pass on, 13 year-old to 10 year-old as they grow.