CANopen transmission to multiple IDs at the same time
In order to control any CANOpen device you should first study the object dictionary of the device. In the dictionary you'll find Service and Process Data objects, which are essentially addressable locations for configuration data, status, control commands etc.

So, instead of trying to figure out what CAN messages to send and how to send them, you should learn how CANOpen works first, find communication objects that you need to access and then send messages in CANOpen format to perform the functions that you need.

Most likely these won't be messages "button A pressed" or "button B pressed", but rather something like "Node NNN Change object 0x6063 to value XXXX", which will be interpreted as "set new speed for left motor".

There are many communication profiles used in robotics, like CiA 402 (CANopen drives and motion control profile). You robot might support one of them.

If you do not know the object dictionary of your specific CANOpen device and do not even know if it supports one of the standard device profiles than there is very little you can do.

From your question it seems you have some kind of remote control device and you attempting to reverse-engineer the communication. This could be tedious process, since some CANOpen commands require several back-and-forth CAN messages to do something. My only advice in this situation would be to try and get the datasheet from the manufacturer.