I took my 5 yr old granddaughter who is also called June and 'Junebug'. My June also has a wonderful science imagination but nothing was suggested in the scope or reviews about the 'darker' side of the movie. Very distressing for my granddaughter who has been separated from her mother for many months now. Wonder Park does have far too many darker moments, so I would not recommend taking an emotionally sensitive child or a child living with grief or living loss.
It would've been such a sensational movie, and quite doable with the long darker side.