Robin2:
The nRF24 modules are very reliable if they are used properly.I don't think your attempt at simplifying the project description is actually helpful because it may be introducing timing complexities that need not exist. Using wireless to detect who presses a button first is not going to be reliable because if the second wireless starts transmitting before the first one finishes both messages will be garbled.
Is it practical for each of the slave Arduinos to store a record of the "hit" data and pass it to the master when the master requests it? The master can poll each slave in turn several times per second and that will completely eliminate the risk of data collisions. The two slaves will need to have very closely synchronized clocks if you want to know which "hit" comes first. The communications from the master could probably be used to synchronize things.
Have a look at this Simple nRF24L01+ Tutorial. It includes an example with a master and two slaves.
...R
So instead of sending if there is a hit from each slave have the server pull for a hit status and time stamping each pull request would probably help synchronize the two boxes. Although wouldn't mean the current draw would always be high (eating away precious battery life)?
What about this. Using two transceiver chips on the master board that listen to each slave separately. That way it can still be time stamped to help synchronize but also eliminate the constant pulling.
- Yoseph