Will getting my new iPad engraved delay its delivery?
In my experience, yes, there will be a delay.

The thing is that when you order engraving (at least it was like this when I ordered), Apple does it in a factory somewhere in China, and ships it from there, which takes forever (it took a little more than a week if I remember correctly to ship it to New York).

If you don't order the engraving, Apple can send an iPad that they have in stock somewhere much closer to where you are, which will be faster.