In Las Vegas, and all casinos that we know of, the cards in Let It Ride are dealt three at a time. That's because Let It Ride is dealt from an automatic shuffler that dispenses the cards in threes, so there's no other option. Packs of three are dispensed one at a time and delivered to each player in turn, then the dealer discards one from his pack and keeps the other two.
Church- and other charity-gambling entities don't have the money to spend on auto-shufflers, so LIR games are dealt from the hand. This allows the option of dealing three at a time, one at a time, or even two-and-one (or vice versa). The good news is that it doesn't matter. As long as the dealer doesn't see the cards before they're dealt, he has no way of knowing which method would be best for the house and can't affect the outcome by choosing one over another. In short, each method is equally random.
As an aside, the main concern with charity gambling for players isn't the possibility of cheating. It's that the payouts in some games may be lowered from the standard, which means the house edge tends to be higher in these venues than you'd face in a regular casino.
