with 2 freshman, i typically practice the new set all season and play the old set all season. 1 season of IQ is not enough to catch up with just 2 freshman, especially if you can bury them on the depth chart for the post season (not sure if that FB is paired with press or not - but even if it is, and those 2 freshman will play a ten or so minutes each even on motion - you still are typically better with motion). next season after a lot of your team graduates, you may even still be better with FB, but that would typically change within 10 games or so - so i think a good rule of thumb is to play 1 season at the old offense. until you start to get past 4 freshman or else if like, a couple of them are going to start - or maybe you took a sim team and all the non-freshman are pure trash or something - its typically going to be true for most teams, that the NT in season 1 of your O/D switch should be played with the old O/D.
as a reminder, playing an offense does not increase the IQ growth rate, so there is no consideration there.