Since the outlets have yet to be installed (30 amp). It was merely mentioned about using 50 amp outlets instead. Since the original poster seems to have some smarts, I'm sure he would use the appropriate conductors to handle the ampacity.You can connect the LOAD, but everything in the circuit (wiring, receptacle rating) must be rated for the overload protection to which it is attatched. Since he is using 30 amp receptacles (and probably ten gauge wire), he cannot use more than a 30 amp breaker. To do so is against code and asking for a fire.
Better to oversize a circuit than undersize. I would go for the 50s. Of course take into consideration the existing service panel and the load it currently supports. And what can be added.