The nRF24L01+ transceivers provide half duplex communication between pairs of nodes. You can't use it directly to implement a broadcast or multicast. You could potentially get the same sort of effect by having each node poll a time source which returns a timestamp, and then halve the RTT of that poll to estimate how long ago that timestamp was current and set the local clock from that. Given that the clocks would only drift slowly once they were synchronised, this polling would not need to be very frequent. Any node which has established its own clock by polling a time source could itself act as a time source for other nodes, but the more 'hops' there are between the original time source and a given node the less accurate its clock will be. This means a flat hierarchy would work better than a deep one.