The fledgling defender represented Wales under-16s in the Uefa Development Tournament in Greece last month.
The Dragons finished second in their group, with Rew starting his side’s 1-0 victory over Russia and 2-0 defeat to the host nation.
Kelly believes the Gosport talent will benefit from the experience.
And the Blues academy chief feels Rew’s call up is a testament to the club’s youth department – and international scouts are again taking an interest.
‘Harvey’s been away out in Greece and he did very well,’ said Kelly.
‘He ended up captaining Wales in one game for a little period.
‘That was good and it was a great experience for the kid and great exposure.
‘He thoroughly enjoyed the experience.
‘It’s nice to see some of our players getting that international recognition again.
‘Jack Whatmough, Adam Webster and Jed Wallace have played for England at junior level.
‘With what’s going on across the board and with the amount of productivity we have, there’s a real interest in the football club and the youth department.
‘On an international level we’re seeing a lot more scouts turning up to watch.’
Six schoolboys were included in the Pompey Academy squad that drew with AFC Bournemouth last weekend.
Leon Pitman, Haji Mnoga and Alfie Stanley started, while Harry Kavanagh, Stan Bridgman and Ethan Robb were on the bench.
Kelly believes all of his under-16s bring ‘something to the party.’
‘The under-16s have been doing really well,’ he added.
‘They’re a really strong group together and have a nice mixture of power and technique.
‘Everyone individually brings something to the party.
‘That’s why it’s nice for all of the under-16s who played against Bournemouth.’