Rottnest Island with Kids

Hey Reddit

A bit of advice please, we'll be in the area in early-mid December and considering a day trip to rottnest. We will have a 8 and 4 year old with us. Bike riding ability ok (except the 4 year old who is still learning). Kids resilience...fairly low...especially in hot temperatures.

Should we do a day trip to Rottnest? Are we guaranteed to see Quokkas? Or are they a night time thing? Would be we ok to ferry over and then bus around instead? Is there much to do besides swimming and the (possible?) wildlife? Is it worth the cost?

Just wondering whether we are better off doing a day trip down the swan to fremantle and having a look around and being a bit more in charge of our own destiny especially with a 4 year old.

Some context - we live on an island in NZ which is approx 40mim ferry from Auckland (Waiheke) so beach life is daily normality for us. Just not entirely convinced. Opinions please!

Thanks