My little girl is 5 and has done a bit here and there with me (mainly bait fishing) on our last trip to Uist she fished using a fly rod out of the back of a boat (don’t tell anyone though

), muddler on a dropper, Goats Toe on the point (her choice) and she was in danger of out-fishing dad at one stage! I didn’t have a boat seat for her so strapped her car seat onto the boat, she wore a buoyancy aid obviously, and had her wetsuit on for good measure. After she got bored fishing I found a shallow sandy bay and we spent some time doing ‘falling in’ practice so if she ever hit the water she would have some idea what to do, hence the wetsuit!
She practiced casting in the garden trying to land the fly into a bucket about 5 yards away and at the end of the week she also caught her very first ‘all by herself’ fish on the fly from a tiny hill loch. It was a browny about 6” long and she was really annoyed that I wouldn’t let her chap it!
Kit wise, she has a cheap Fladen 7’ 4 weight with a cheap Shakey reel and line, she’s on her second rod, she broke the tip on the first when she was using it as a magic wand one day! From the bank she doesn’t wear any additional buoyancy but she is a pretty strong swimmer and very confident in the water.
If we go fishing then I don’t normally plan on doing any fishing, my time is spent unknotting things and picking stuff up that she’s dropped (no matter where I put anything, she can knock it over!). In the boat the wife was with her so I got to do a bit, I spent most of my time watching her though. I try to get her involved as much as possible, setting up the rod, choosing flies and pointing out other birds and animals etc. The most important thing I would advise is don’t go if the weather is at all dodgy and when they say they want to pack up, pack up straight away even if it’s only been ½ hour. Oh and take a nice packed lunch!