Drill it through and put a long carriage bolt with a nut on the other end in its place?

I would take some wooden bbq skewers and wood glue and put a few of them in the holes. This will effectively make the hole smaller.

Alternative is to drill the hole out enough so it can tightly accommodate a wooden dowal. Once that is glued in place, you can drill the proper size hole for your lagbolt.

And washers on both ends.

Yeah skipped that part. For sure, washers are critical putting a bolt on wood.

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A stripped lag bolt is a pilot hole for a larger lag bolt!

Kidding sort of… It would work but a carriage bolt would be better.

And domed nuts, to make it safe for the kids.

First, give a good tug at those posts. If the holes are stripped out, there might be rot in those holes, making the post weak.

If it's still strong, then go with what ThisIsJustForPornog suggested.

Or at least cut the bolts flush with the nuts. And washers under the nuts, but not under the head of carriage bolts, which have a square shank to resist turning in the wood, so you can tighten the nuts.

Good luck driving straight through the entire bolt. I'm looking to see if a long 1/2" or 3/4" core bit exists. core the whole thing out, can't find any, maybe a diamond bit with slots cut in.

Are you saying a 24-36" long 1/2" or 3/4" drill bit?

Main reason I call them lag screws, refuse to think "bolt".

i'm saying a 6" long core bit. Core out the whole lag after popping the head off.

OP said is saying the wood is stripped out around the lag screw, not that the screws cannot be removed…

Ok well they need something to grip maybe drill a 1/4" hole alongside the lag then hammer in a 1/4 dowel so the lag can grip and pull itself out.

That or try to find out where they would come out the backside, use a forstner or something to find the tips and push them out while spinning them.

Drill and tap the head for a 10-24 2" bolt. throw a tack weld on them cut the head off the bolt, close a drill chuck on it and spin it in reverse and pull.

Drilling things out like this is a PITA, you'll never get it right and by the time you are through the hole will be 3/4" from the drill wandering all over.

You are way overthinking. This is a lag screw in wood. The screws can be removed pretty easily. Just put a screwdriver under the head and back it out. Then they just need to drill through and install carriage bolts.

no kidding needed I think this is the right way

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Washers on carriage bolts on the head end? Those have square ends on the inside, you'll have to go way up in washer size.

Why/how would you put a washer in the head end of a carraige bolt? The whole point of a carraige point is not to

That seems way more hassle than just going up to the next size up lag bolt

Whenever I had wood stripped out, like a door striker plate, etc., the solution was wood glue and toothpicks. Suspect the same concept on a larger scale would work.

As someone who still has a scar from when I was 4 due to non-domed nuts.... That shit hurt. Been 30 years and I still remember it.

I've drilled holes for carriage bolts in a 2x10, narrow side (as in 9.5" long). Had a 36" bit typically used for installing electrical cables, was easy.

Easy way... Get a stick, or shim and glue it in the hole with CA glue. Do not fill up the whole with the shim. Screw in the lag bolts back in. The CA glue will strengthen the wood, the stick or shim will make the hole a little smaller so that the lag bolt will be tight. Look up CA glue with activator on Amazon. I use this glue quite often.

Video on CA glue. https://youtu.be/V23s-VQETBs

Cedar is a very soft wood, lag screws will easily pull out, best way is to put a eye bolt with a large square washer at the top to support the weight from the swing.