Hold up. Even though your tank is cycled, you should never add so many fish to the tank at once. You'll cause a huge ammonia spike with the massive added bioload and may lose some fish...at best, you'll have to seriously monitor ammonia levels and do like daily water changes until the tank can settle itself. I would add just the 10 labs first, give it a couple weeks to settle, then add the cobalts.
But yes, in theory, a larger pleco should be okay with them, but you never know for sure. I've heard plenty of stories about plecos living with mbuna successfully, but I've heard a lot of mbuna eating pleco stories, too.