Cuban has sold the Mavs to Adelson-Dumont Family

[F Gump]

What happens if the casino stuff fails to pass?

Even if it passes and the Mavs stay here, how would it work with a minority owner running the operations and spending the money of the majority owner?  The Adelsons didn’t get rich by being dummies.  There has to be protection in the documents for them to not just be Cuban’s piggy bank without any checks and balances.

These are good questions. It's reasonable to assume both parties have ultra-smart people to examine the what-if's, and then figure out how to structure the deal so they both have fair protections.

"There has to be protection in the documents for them to not just be Cuban’s piggy bank" -- 
a. Yes, their protection is in the sale docs, which will define the terms of the partnership, and the consequences of the interest that Cuban still retains.
b. The idea that Cuban has "control" is looking like sloppy reporting, because Adelson (not Cuban) will be the 'Governor' of the team, making  Adelson (not Cuban) in charge in all NBA matters. 
c. Generally, it sounds more like his role of running the team is a job he is filling (at least for the time being), instead of them, because they think he is capable and they are not.
d. As far as his ability to get into their pocketbook, there are partnership norms that probably come into play that help. For example, let's say the ownership is a 60 (A)- 40 (C ) split. If/when Cuban wants more cash money injected into the team to do this or that, or the cash flow comes up short (say for big contracts, or luxury tax) then he would have to bring 40% of it himself. (He starts off with over $2B in cash on hand, minus taxes, which should allow him the opportunity to spend if he wishes.) And as an underling, it's close to certain his spending of team money will be audited, he will get a designated salary, and he can be fired for mismanagement if they ever feel the need.

On the casino question, that may be a tougher nut to crack than they hope. At the same time, they may be betting on the idea that should the laws stay the same for now, but then WHEN the laws in Texas eventually change (if they do), this setup may be creating a huge head start for themselves at being 1st in line for a casino (or even 5 or 10, eventually).