I don't have kids, but I've taken plenty fishing, many for their first time and I've gone fishing with kids as young as two.
A couple of things I learned...
It's not about you. It's also not about trying to make them anglers for life, it is about having fun that first time and seeing if they ever ask you to go a second time.
Leave your rod in the car.
Rock throwing and general disinterest is to be tolerated.
Combine the fishing with a planned picnic or other activity to see if they get a second wind WHEN they get bored.
As tough as it is, leave to go home when they say they want to go home. A quick antidote in this regard on a trip to a small local pond with a former GF's two year old son...
Excitedly he woke me up at daybreak, I made him breakfast, packed the car, put him in the car seat and we headed off to the pond which was about 15 minutes away. We unpacked, got started fishing, caught some fish and in about 20 minutes or less he said he wanted to go home...
And we did.
A technique tip:
I used to fish with a bunch preschoolers belonging to some friends at a small pond. After watching them struggle with the concept of timing and setting hooks, I decided to help them out without their knowledge.
After the cast, I would kneel down or stand in front of their rod and secretly grab their fishing line past the tip top. When the oblivious kid didn't realize it was time to set the hook, I'd do it for them by jerking hard on the line in my hand.
If the hookset was successful I usually say, Hey I think you got a fish, reel it in!!" That was followed by screams and smiles all around and they were none the wiser they had help. 😉
Tackle tip:
When fishing with some different kids with the similar timing and hook-setting issues I had an epiphany...
Circle hooks...
You won't find them in a fly shop and the small sizes can be a challange to find. However, because I also fish bait, when I went home I tied up some simple nymphs on some small circle hooks. The next outing I also brought along some bait holding versions.
Once I got the kids on board with reeling in versus setting the hook, the fish were hooking themselves. I also UP-SIZED the float so it offered more resistance to the fish which results in some automatic hook-sets.
Try circle hooks sometime, you and your kid(s) will be pleased with the results. 😉
Have fun!!!