Two things I would consider if there is not an itinerary jumping out at you.
1) The weather what kind do you like? -For example I didn't really want to do Southwest Splendors or Italy in the middle of the summer. I live in a hot area -and I want something a little cooler if at all possible.
2)On the trips where you stay in the national park hotels -I understand these will be a bit more rustic. (No A/C , no TVs in rooms etc...) -something to consider if you think this may bother you. This is not an
ABD issue -I understand all national park hotels are like this.