The Fluid 4.3 is an awesome bike, one thing I found though is that the head angle is a little steep for the bike park (not bad, but not perfect). I found a used Fox Talas 34 (32 would have been better, but I had to go with what I could find) and had it lowered. Now in the short travel settings the geo is the same as the OEM form, but in the long travel setting he's got a comfortable DH-centric head angle. This change wasn't cheap (though not nearly as expensive as you might think) but it's had a surprisingly positive affect on his riding and the variety of trails that he can handle (and therefore a lowering of Dad's boredom doing the same trails again and again and again).
The Maxxis Snypers were much more competent that I expected, until it got really muddy. A little bit of mud wasn't too bad, but mucky trails in Squamish in the winter probably won't respond well to them. Consider some High Rollers (if you can find them) or source out some old stock 24" tires collecting dust from back in the day when we all had 24" rear wheels. The Fluid has a surprising amount of clearance so you're not too limited in width.