If you have doubts, you might wish to consider contacting airportgenie.com which is a service that is provided for passenger accompanying at Dublin airport. They may be be able to assist you sone for a fee.
Having said that, if he is a confident young man, he should have no problem with transfer at Dub. The transfer desk is well signposted and all in the one terminal (T2). He’ll be able to pre-clear US immigration as well.