Bonjour Tom,

If the question had specifically asked for "What time" then, yes, the answer would have been "À quelle heure est-ce qu'on arrive ?".

Also, in this context (i.e. children asking when they'll arrive at their destination), French children/teenagers would use "quand" instead of "à quelle heure". It is that go-to-expression they use ! (Believe me, I have done it plenty of times as a child ;-) )

I hope this is helpful.

Bonne journée !