The Royal Hawaiian (also known as The Pink Palace of the Pacific and, alternately, the Pink Lady) is an odd structure for Hawaii. Opened in 1927, the Spanish style architecture is not what you would expect for a beachfront Hawaiian hotel. One of the first hotels established in Waikiki it quickly became the place to be. The six-story building sports 400 rooms and cost over $4 Million dollars to construct. It was the first place to ever to be called"The Western Whitehouse" as FDR conducted a bit of presidential business inside it's walls. The architecture, a mix of Spanish and Moorish design, was said to have been influenced by the Arabian movies of Rudolph Valentino. Pink was kind of in at the time, so I imagine that the decision to paint the place pink was a no-brainer.
Grenadine was originally prepared from pomegranate juice or something similar. The most popular brand of grenadine is a corn syrup nightmare called Rose's which I wouldn't feed to hungry ants.
So, to imagine the Shirley Temple as was prepared at the Pink Lady you would have to imagine something totally different. If you wanted to try and approximate it you would need to do some searching for the right kind of ingredients. First place to start would be the Ginger Ale. My research indicates that the closest thing you will find to real ginger ale is Vernor's which is made and bottled by Dr Pepper/Seven Up Inc. and is produced close to the recipe originated by James Vernor that was a mix of 17 ingredients including ginger and vanilla. I have had it and it is good, however something that I have heard which might be better is Fever Tree Ginger Ale. I have not tried it, but it has been highly recommended to me.
For the grenadine, try making your own. It's pretty easy (I say this never having done it, but it SOUNDS easy). Grenadine can be created by simmering pomegranate juice for 15 minutes on the stove, then adding superfine sugar.
I have discovered the most wonderful grenadine from a company called Employees Only. We have started using it in our very own music venue to produce what we call an authentic Shirley Temple and I can say that anyone that has tried it has been amazed at what this old standard of a soda ca taste like.
I guess the easy thing to say is "Why bother". I mean, this is a drink for kids right? Well, I firmly believe that kids need to be trained to expect higher quality at an early age. I mean maybe the decline of the Shirley Temple had something to do with the decline of the tropical drink. As things got sweeter and sweeter people just started taking all kinds of liberties with their drinks. If you accept some combination of cola and Sprite mixed with a sickening red syrup as a Shirley Temple, then is should come as no surprise to you when the Mai Tai you ordered ends up being Hawaiian Punch mixed with Bacardi (I've seen this, I know it happens).
I think it is worth, at least once, to mix up a proper Shirley Temple and whisk yourself back to the days of the Royal Hawaiian. I can feel the ocean breezes now.