April it will be starting to cool down, one or two hot days maybe. Perthites wouldn"t class it as swimming weather, but Melbournites might.

Freo is a good place to stay but it can be exxy, also depending on where abouts in freo, you might have a few late night revellers around as well.

Plenty to do in Perth, it is a very family place and if you are willing to drive, there is a lot to do within about an hour or two travel time from Perth. Beware Perth works differently on Sundays. Only some tourist precints are open, otherwise everything else is shut.