For the money a better bridge would likely cost vs 2nd hand DSLR, I would probably be inclined to pander to the lads aspirations and get a DSLR... as cheap as I could. Probably yet another D3100 as I acquired for my daughter when she started GCSE and O/H when she started to feel left out!
Bridge cameras, in generalities, can be very useful, user friendly and a lot of bang for the buck, but they are peculiarly restrictive and Skateboarding.. well, juit KIDS come to think of it, but Kids on Skateboards? That's heading into the realms of specialization of dedicated action photography stuff.
Bridges tend to offer an awful lot of zoom, awfully cheaply; BUT the niggle is that they tend to have peculiarly slow lenses; they may be quite fast at the wide-side, perhaps, f2, though more likely f3.5, but by the time they are racked out to telescope lengths, that aperture can be as little as F8 or f10, seriously hampering faster, quick-kid-on-a-skateboard freezing shutter speeds and begging ramping the ISO..... Skateboard parks tend to be beige-blocks of concrete with little colour or contrast; this would tend to give focus a harder time hunting for edges to get a red-dot on, as well as making it harder for the software to differentiate 'levels' between shades, exacerbating issues of noise, so ultimately more cons than pro's to the set up for that genre....
Its the middle of July... there's not sooo much school-summer-holiday remaining, when he's more likely to spend all day every day down the park watching sk8erbois... what then? And when leg out of cast; how useful the zoom when he can zoom with his feet? Most of the sk8er photo I have seen has been shot, not with a tele-photo, but up-close and personal with a wide, or ultra-wide, or even a fish, especially getting inside a half-pipe, and reveling in the action and perspective. To my mind, this would seriously limit the benefits of a mega-zoom bridge even further; lots of zoom is likely not a benefit in this genre, and of peculiarly short term use.
A 2nd hand DSLR, and the D3100 and D3200 are noteably compact and barely any heavier or more bulky than a bridge; has the ability that..... oooh, come Christmas perhaps, to take alternative lenses, and where kit 18-55 has proved limiting, something wider could be the 'next' present, to give him something to bolt on and off the front to feel he's really got the SLR 'thing' in his hands, and perhaps encourage some progression in the pursuit, where I would be afraid that a Bridge would be a one hit wonder of limited short term value, he'd likely ultimately be disappointed with, if not feel slightly 'cheated' it wasn't like the big-boy camera his mate uses, and all the derogatory comments about what it wont do... with an SLR it would be derogatory comment about what HE couldn't do, in which there's scope to break the kiddie boundary and 'some-one' to interact with him, and encourage him to learn how to get more from the camera, rather than just do the teen thing of moaning, griping and blaming the camera until 'some-one' spend more money on him....
Kidz will still be kidz... and he may still retreat into kiddie-zone of bedroom with play-station, magazines and MP3.... but, an open door to encourage him to talk to 'some-one' be it a groan up of mate into photography, not necessarily to learn about f-stops and shutter speeds and Depth-of-Field technicalities, but at least with the tools that would let him if he is inspired by getting results that encourage him, and do more often impress his mates on farce-broke.
Which is all to look at a some-what bigger picture and alternative angles... but that's what photography is all about.... and that's how I'd approach the matter; and £150 on a 2nd hand DSLR, with kit lens, is a lot cheaper than £300 on an over the counter bridge, and likely to offer so much more, as well as leave pennies in the pot, to perhaps even get him another lens off the batt, if zoom really an imperative here and now, a kit 55-200, might only add £80 and still leave pennies in the pot, if going forwards in sk8er photo, a 10-20, might only add another £120ish... whole lot could be procured for the all in price of a better bridge... or split up, to keep interest going, and cover Christmas even.
A £150 2nd hand DSLR is also a much less bitter pill to chuck away when he comes back complaining its been dropped off the top of a half pipe! And kids DO break stuff... as his leg is testimony too! lol
