Taking my son on a daytime 10h

[Patudo]

on those daytime trips it's mainly lane snapper and smaller mangrove snapper, with plenty of grunts and porgies coming over the rail too. Small grouper appear occasionally. 

Bottom fishing in 60-80' of water. Preferred method seems to be knocker rigs or chicken rigs with cut squid, threadfins, and shrimp.

The debate is do I wanna bring him a spinner so its something he already knows how to use, and I don't need to worry about spool overruns. But I suck at fishing a spinner offshore.

Based on the above info, I would use a medium spinning rig with maybe 30-40 lb braid, or maybe 20-25 lb mono if boat policy disallows using braid.  In that depth you should not need much lead to get to the bottom, and detecting the lead hitting bottom should be easy thanks to the super sensitivity of braid.  The low stretch braid will also make bite detection easy, and it sounds like you'll get plenty of nibbles - hopefully enough to keep his attention focused on trying to hook the next one. 

Bring a couple of backup outfits and/or spare spools in case line gets twisted up, or you lose line to snags etc - always a possibility with a beginner.  Bring replacement rigs and leads too. 

If the situation allows it, a conventional rig with 30 lb mono and about a TLD 15 size reel could be worth bringing along, to put out a live bait under a float.  This will probably catch more cudas than anything else, but when I was his age (how old is he?) a 20 lb barracuda would have been exciting as all hell. 

btw - What outfits have you seen the other charter fares using?

[JasonGotaProblem]

I'm gonna have to reschedule the trip, we may switch to the 5h or a different day. And that sucks because weather is looking great.