I would suggest going by the excellent Crete bus service. There are regular buses to/from Chania taking just under 3 hours The Chania bus station is only a 10 minute walk to the harbour. Though I have driven in the Crete countryside without problem, I would not fancy driving in the streets of Heraklion or Chania.
A car would cost you around €30 for one day, the single bus fare to Chania from Iraklion is €13,80 so if there are two of you, the bus ride there and back will cost you €55,20. Obviously there's the cost of fuel to take into account with a car. A small car like a Peugeot 107 would take use much more than 4 gallons there and back which would cost you about €32. If the ride merely entails getting out of Iraklion and into Chania, it's OK, but obviously it's your call. The entire route is along the E75 New National Road, which is well maintained and fast.
Although we always have a car when we are in Crete, for a day out like this I would agree that the bus would be best.
There's lots to see on the drive and, from the coach, you can both take in all the sights.
When you get to Chania you will be able to enjoy your whole day without having to find parking (can be a bit of a challenge although we usually find somewhere) and you can have a drink when you eat if you want.
After a day enjoying the delights of this wonderful city I'm sure you'll appreciate a stress-free air conditioned run back to Heraklion!
Hope you love it as much as I do!
Thanks for your great replies. Just 1 more question. If we were to go by car, would it take the same amount of time, as by bus? 3 hours, each way by bus seems to be a long day. Thanks
Hour and a half by car
Car definately would be faster and withy three of you it is the least expensive option.
Well that is not very helpful Cacofonix.
Although I don't drive in Crete, my OH has, on many trips, with absolutely no problem.
The national road is an easy road to drive and I can't see why the OP should have any problems whatsoever. :O) :O)