We've had some great city breaks with our two kids. There are some excellent serviced apartments around that make life easy to start with - kitchen for making & keeping snacks, in-room laundry, plenty of space without the stress of will we/won't we get the connecting rooms requested etc. As said above, practicality is the key but with an apartment you can eat in or out - whatever suits the mood.

Have so far found great places in Singapore, Vancouver, Perth, Adelaide and San Francisco so am sure there are others too. Assume our kids are typical in that what many would see as mundane things are really quite exciting to them (short ferry or bus ride type thing). Find out where the nearest parks are - again my kids love going to a new park (to me, every swing is the same but what do I know, I'm just an adult ).