We went in August last year, and yes, whilst it can be hot all buildings and cars are air conditioned so if you get too hot then you just go in a shop for a few minutes to cool down. There are often misters in the queues for the rides aswell. Some of the rides have a baby wait station (or something like that) where one parent waits with a baby or young child whilst the other one goes on the ride. Then you just swap over without queuing again.
I'm sure you'll have a great time.