Calf of man - great place for seals, they are all in the sea or on that rock in the middle
and it's really easy to get great shots of them
The harbour at Port St Mary is great for rock pools, rock hopping and photography
At the very top of the island is a lighthouse and gravelly beach. Good spot for photography and you can see scotland.
Peel has a castle your lad will like climbing around and a pretty harbour, plus they make the Manx kippers there. Yummy.
The A14 from the bungalow is a pretty road, Selby reservoir and nice twisty bits with an interesting tea house in the fields at the bottom.
For the Race, depends on the weather. The hills can get wet and gloomy whilst other parts of the island are covered in warm sunshine.
As for the race:
Kates. There's a bit of a meadow you can sit in and get shots. found this pic to show you what I mean
Cre-ny-Baa - I think that's the pub on the corner not far out of Douglas. Usually packed but a good spot and the bikes slow for the corner to give you a chance.
And of course the Douglas sea front at night
Have fun.