I would avoid the questions framed with superlatives (most, best, strangest, etc.) because they require an unnecessary and distracting step, namely, rank-ordering everything within a category. It’s enough just to ask “What did you like about it? What was surprising? What would you like to know more about?” etc.
If I were there with my son during his visit, I wouldn’t go armed with a list of questions unless I were already familiar with the ins and outs of a PBS station and knew what he was going to see. Instead I would go in receptive mode, model my own learning response to it (noticing things, listening, asking questions without hogging the guide’s attention, etc.—as well as showing respect for the environment and the group), relating it to knowledge I already had (or he already had) and processing as I went. I’d point things out to him and pay attention to everything he pointed out to me.
Mainly I would follow his interest instead of prescribing where he should focus his attention.
Afterward I would probably ask my son if he saw anyone doing things he’d like to try himself and also check his understanding with queries such as “Do you know why they…?” and “Did you notice…?” I would suggest following up areas of interest with a little research and then leave him to it; if I pushed, I know it would kill his enthusiasm by making it my thing instead of his.