I don't think salmon fishing is a good way to introduce 7-9 year old kids to fishing. I know this from experience. If you get a 7 YO who has never fished before into a coho, odds are he/she will drop the rod in terror when the fish runs. Been there, done that. The other factor is that what we consider "hot" salmon fishing translates to "drop-dead boring" to a 7-9 YO newbee kid. Been there, done that too.
If you want to take them out on the salt and have a crack at salmon while still keeping the kdis entertained, take a dozen 1/0 hooks on heavy leaders, 3-4 dozen worms, a few 1 oz ball weights, a couple dozen herring, and a few mooching rigs out to Possession Bank. Start the kids out on the bottom at the western buoy in 40-60' of water with a worm and 1 oz weight. They will start catching flatfish immediately. These flatfish are usually 1/2 to 1#, but can range upwards of 3#, so they aren't little toy fish. They also happen to be really yummy. You may snort in disgust at this point, but guess what, the kids will be having the time of their lives. They might even get to catch a SHARK!! Once they get comfortable doing that, you can sneak a mooching rig into the water for yourself and maybe scare up a coho. If you catch one, and they want to try, no problem, just clip a mooching rig onto their line and away they go. If they get bored of that (usually takes 2.6 minutes), you can switch them back to worms on the bottom.
The alternative is to take the kids out, tell them to stay out of the way while you set up the kicker, downriggers, and rods, tell them not to touch the rods and just sit and wait, then watch them try to bring in a feisty coho that more than likely will spit the barbless hook because of course the kid has no idea what he/she is doing.
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Regards.
Finegrain
Woodinville