Suppose that DHCP server broadcast its DHCPDOFFER message to its network, for one particular iPXE client. But at the same time, there's another iPXE client also waiting for DHCP server's reply. Will both client receive the same message and as a result, one recieves incorrect message?
No, the DHCP protocol takes care of differentiating between different clients requesting information at the same time. The packets contain a transactional identifier that takes care of avoiding responding to the wrong client. On the other hand, make sure you only ever have a single DHCP server on the same network. There are some links to useful resources on DHCP protocol over on
http://networkboot.org/.