It's a fabulous view and a beautiful place. I suggest you get there early as the walk up the hill with children is devastatingly hot. Luckily there are lifts from the museum up to level 6 which is the Basilica itself.
The Basilica is beautifully decorated inside, the history and view are lovely and you get a real sense of Marseille's position. Now here's what we did to come back, forget the comedy tourist train or the bus, we got an uber car which was 9 Euros back from the Basilica to the Panier district for lunch. The comedy train would have been 12 euros, hot and cramped next to sweating tourists.More