Stephenson started the game, while Olver came off the bench to kick England's final three points in the 25-13 victory. Hobbs also came on as a second-half replacement.
The win rounds off a faultless season for John Fletcher's side, having already achieved wins against France, Scotland, Georgia and Wales.
Speaking after the 25-13 victory, Fletcher said: "We've gone unbeaten all season which in my eyes is a Grand Slam, we're really pleased with all the efforts, and it's not just this game - it's been throughout the campaign.
"A lot of these guys were in the Under 17 squad last season and they've come through and worked extremely hard and they deserve this win against Ireland. They deserve everything they get. Their effort, commitment and work rate was excellent and considering the nature of the game it was a really good performance."