They should be able to coexist without any significant problems. There is an unlikely possibility that a pistol shrimp may capture and consume a cleaner shrimp if it wanders too close to the pistol's lair, but my experiences suggest they can cohabit an aquarium. Of course, my experiences are based on tanks larger then your 29, so take my suggestions with a grain of salt. The proximity of the two might cause problems, although I still think it's unlikely.
Yes, you can keep them together with a couple side effects. I have skunk cleaners, blood cleaners, and a Scott Michaels pistol shrimp in my 105. When first introduced the pistol spent all it's time under the rocks in it's burrow. Now it is more comfortable and is all over the rocks. Now that the pistol is out and about the other shrimp keep their distance from it since it will clip their antenna when they get close enough. In a 29 the other shrimp will not have as much room to retreat from the pistol if need be. Just something to consider.