Yes they should be great with your betta! I would add the less teritorial fish first, like tetras or corys first, then the betta and then the cockatoos. cockatoos won't buly other fish, they make a little cave or hole into their home and guard the gravel a few inches from it. the ussually won't harm any fish or even bother them if they swim near by. occasionaly the male might come out and put his dorsal fin high to scare fish away from his home, but that's ussually it. i'm not sure if you should put the bolivians in too, since they both have territories. but if it's a big tank, they will be fine, and should live in harmony! you want to make sure to add two or three fish and no more than that when adding fish to the tank, that way. the bacteria can get used to the overload. Oh and make sure to Quarentine, quarentine,quarentine! this will save you alot of stress, hassle, and fish!!!!