Believe it or not, the mobile version of Google Maps hasn't had support for multiple destinations. You could plan that multi-city tour on the desktop, but you'd still have to navigate one stop at a time on your phone. You might not have to the next time around, though: Google is quietly pushing what appears to be a server-side update to Maps for Android that lets you set multiple stops. You can navigate to a tourist trap, a restaurant and your hotel without having to enter fresh directions every time.
There's no word on iOS support yet. Also, whether or not you'll get it on Android is arbitrary right now -- just having the latest version of Google Maps doesn't guarantee that you'll see it. It'll likely take a few days before the multi-point feature is widely available. So long as you can wait, however, you'll have just the tool you need to plot that lengthy road trip.