Sorry No.
The cap is a tough river and fairly dangerous river to fish. It's also not that easy to catch fish there.
It's currently full of stale coho, although with this rain a few more fresh fish will have come in. But I would not recommend it for kids. Sorry.
None of the other rivers offer any decent fishing.
TBH, the best place for kids in North Vancouver is Rice Lake.
There are still some fish in the lake left over from the Fathers day stocking.
The easiest method for kids is a sliding weight, swivel and about a 2-3 foot leader with no 4 or 6 hook and use chartreuse coloured power bait that floats.
Follow this set up, but do not use a treble hook! You must only use a single hook.
https://www.youtube.com/watch?v=U6IewE4gXv4Fish off the dock and cast across to the small island in the middle. Make sure they watch the rod at all times and strike as quickly as possible, otherwise you will end up with the fish swallowing the bait and if you do not want to retain the fish you will do them a lot of harm. Also use barbless hooks so that you can return any Coho you catch. You must not retain Coho, only keep the trout.
Hope this helps.