(1) If this is a recurring issue, you might want to consider tools like cfengine and puppet, which are designed to automate system administration tasks for large numbers of machines.
in reply to net::telnet problem
(2) If doing 50 concurrent file transfers causes unacceptable network congestion, you might consider using the bit torrent protocol to distribute the file internally from a local server (like Bloodnok's suggestion, but with a different protocol). Bit torrent is effectively cooperative so that the entire 50 GB does not have to come from a single source (host).
(3) Finally, let me pile on the anti-telnet bandwagon. It is simply a bad idea to run a telnet server in most circumstances. If ssh seems to have too great an overhead, you can greatly reduce its overhead by using a weaker cipher (eg, "ssh -c arcfour hostname"). This does not affect the protection given to the authentication mechanism.