The in laws

I agree with the others about the fishing. You cast it for him, but let him have the opportunity to catch something. Watching you catch fish while his line just sits there won't be any fun. Once he's reeled in, you can start showing him how to cast.

Other activities: photography - a cheap digital camera can get them very excited about the outdoors. A scavenger hunt. Get a book on insects and go bug hunting and identifying. A tree identification book.

I also agree with letting them help with setup, take down, and all that's in between. Kids under 9 are eager to help and want to do a good job. Let them sweep out the trailer, let them help plan the meals, and so on. They'll love it and will remember that for years.

My niece still remembers the time she "slept on the kitchen table bed" in our TT. And cooking her own hot dog on a stick over the campfire.

A float and a hook. You cast it in and let the child reel in the fish hopefully. However the 2 year old might be a stretch to entertain other than playing in the dirt. :)

Scavenger hunt is good. Different colored rocks, leaves, etc.

Wiener roast, smores, firewood gathering, hiking, license plate searching for different states if they are a little older.

Bamboo pole

If your worried about him casting out a line, let them use a bamboo pole
I still like to use one with my grandaughter

I vote with give the boy a hook.

I was about 5 and my first fishing pole was a stick with a string and hook tied to it. I actually caught a little lake perch off the edge of the dock.

And I Knew The Rules. Any flinging, stomping on the dock or loud voices meant no fishing.

Almost 60 years ago and I still remember the thrill of that first fish.

Is the room to take their bikes? A scavenger hike through the woods looking for specific trees, plants, bugs and birds can be fun.

I must say, I agree with BTPO1. If you want the 4 year old to want to go fishing again, he needs the opportunity to actually catch something. That 4" bream will be the beginning of wanting to go fishing. If he doesn't catch something, and he will realize he can't, then sitting still is absolutely NO FUN. I started fishing at a very young age, and by 5-6 I was learning to scale my own. Fast forward many years, and I was able to take my son fishing and help him clean the fish he caught.

Noone has taught him to fish yet so I'd imagine he would just swing it around crazy like trying to cast. Much safer without a hook when i start to teach him lol

I will probably get blasted, but why not let the older one fish with a hook on his line? Both my DD and DS both started fishing around three with hooks. I just needed to pay more attention to them. I would bait the hook for them until they got older, but they were happy to catch something. JMO

Campfire & smores! You can't go wrong with smores. Other than that, explore & have fun. Let them help (or think they're helping) setup the trailer. It turns out little boys like just about everything the big boys like.