The standard rooms are average hotel size (probably around the 30sqm mark) and it all came down to how old / small your kids are and whether they may be interested in sharing a double bed?
There are rooms which are double double beds, so you and your wife could be in one, and if the kids are like small / young they could share the other.
Bathroom wise its smallish but acceptable.
Location to the pier etc is great but is a good 10 minute walk to the Mag. Mile.
Reminds myself to write a review but simply from my recent stay at this W I must say I was unimpressed with this property. I'm not whinging that I did not get an upgrade to a suite but rather the lack of soul from all the staff I encountered esp. the girls on the front desk who absolutely no desire to want to be of any help. They should get off their 'lofty airy fairy cloud' and come back down to Earth - yes Earth - and realise that customer service and a wanting to help is the key.
The biggest question I ask myself is, would I stay here again? Or would I recommend this hotel to my best friend? And I would definitely say No, and esp. when hotels on the Mag Mile can be found at better rates than this W.