I would go for the in hand show as you get to see what he like at an actual show, and hope on him and ride around for experience. Giving him a change as well as a nice day out
within 2 weeks of bear being broken in i took him on a sponsored ride (only the trot one) but that did him the world of good but before i started riding him i had taken him to 2 shows and done inhand classes. its all good experience for them
so do the show and Sponsored ride clash? if not take him to both xxx