Let's begin that using different access points from different manufacturers isn't an ideal situation when using those in one network. But it is possible.
If you use the UniFi and the two MR33's only as a wireless bridge, you can create a big network by using the same SSID on all three access points. With good preparation in location (not too close or too far from each other) and configuration (not too high tx power for example) you can make these three access points working great together.