I am a massive fan of Western Crete - that's why I live here! But I will stand up for Elounda too. It does have several large, upscale hotels around it, & it is mostly tourist based, but it also does have an authentic Cretan style & feel to it. A lovely water-front to stroll along, with a fishing harbour & tavernas (not too overpriced, either!). A super walk is to Plaka, it's flat, along the coast, from where I highly recommend you catch the little boat to Spinalonga. If you know the island's history as a former leper colony, or have read Victoria Hislop's popular book, "The Island", leaving from Plaka on 1 of the smaller boats will give you a better sense of atmosphere. But the bigger boats from Elounda can make a fun family day out, as they stop for a swim/snorkel/barbeque too.
A nice trip out is to the village of Kritsa, a large, traditional Cretan village, with many souvenir shops! It's a pretty drive, & don't miss the church of Panagia Kera - the most jaw-dropping 13th C frescoes I have seen. You may want to also visit the ancient site of Lato, in a beautiful position up in the hills. A short drive to Plaka & onwards, up hill gives you some super views & countryside.
Nearer Chania, Imbros gorge would make a good option for a trek for you - it's about 8km, do-able by kids who are used to walking. It's easy by car - you park after Imbros village (on the road to Hora Sfakia), at Komitades at the end of the walk either ask a taverna to take you into Sfakia for lunch, then you can get a bus back to the car, or you can get a 'taxi' (pick-up truck) to your car. It's a great day out, incorporating magnificent scenery, walk, nature, lovely coastal village & great food!
Re driving times - roads are small & bendy, you will not be going fast! Other than the National Road, along the north coast, most other roads are very slow, often hilly. Over-estimate how long you think it will take