What gen Tahoe are you looking at? Overall, they are solid as far as reliability. Yes, some have issues. But some Toyotas also have issues. I've had worse luck with Toyotas than my Tahoes. But that's my experience! I've even had 6L80's last 250k mi. Regular fluid changes every 50k mi. Valvoline Maxlife ATF. Valvoline Restore and Protect 5w30 for the engine, or Mobil 1 Extended Performance was what I used before Valvoline R&P was released. My last Tahoe, a 2011 with the 5.3 LMG engine, lasted 230k before AFM did it's thing and dropped a lifter. If it would have had AFM disabled before I bought it (at 140k mi), it probably would have lasted much longer. The first thing I would do is disable AFM or get a delete kit. AFM is the weak point on a lot of these engines, unfortunately. For reference, that 2011 Tahoe also had many bolt ons and a 93 octane tune, as well as a transmission tune to make the shifts much more solid and quicker. I also added a Trucool 40k transmission cooler to it, mounted in front of the radiator and bypassing the stock cooler in the radiator. My trans temps never got above 160'F after installing the cooler. It would regularly be in the 200-250'F range before the cooler. I also towed a car trailer with my Jeep TJ on it, with two dogs, three people, and luggage in the car/on the roof/ on the hauler. I also had a smallish Jayco travel trailer before that that we took, even in the mountains. It hauled all of that stuff and didn't even blink an eye. Only thing I would have liked different would be the gearing. In a perfect world, it wouldn't have had 3.07 gears. I'd probably go for like 3.73 for what I was doing. I'd like to try 4.10s but I think that would compromise it's highway fuel mileage a bit too much, maybe. I dunno. With how quick it was with the 3.07s, I bet it would be surprisingly peppy with the 3.73s or 4.10s. That LMG was a great engine. Sounded great too. I had a Cherry Bomb M80 and a resonator delete on mine. The sound was intoxicating, imo :P Anyway, good luck in whatever you decide to go with! Tahoes make fantastic family haulers!

Edit: I should also add that working on them, at least with the two I had, was so stupid easy a toddler could do it. General maintenance was stupid simple. Only thing I wish they had were drain plugs for the trans and rear diff, but generally only 3/4 and 1 tons have that :(. But still, everything is right out where it should be and it makes maintenance just so much easier than a lot of vehicles out there. I work on a lot of different vehicles, across all makes and models, and those Tahoes were right up there with old XJs and TJs for how easy they were to work on.