What's The Best Way To Introduce The Puppies To A Crate?

To reduce trauma, I'd suggest the following:

Introduce them to the crate by placing a few small treats in the crate.  If they are too young for treats, you can try placing just a little bit of food or puppy milk in the crate.  Sit them just outside of the crate.  If they find the food own their own, great! If they don't, then pick them up and place them in the crate near the treats/food/milk.  Close the door and leave them in the crate for a brief time, then take them out again and immediately take them outside to use the bathroom.  Keep trying this over and over again throughout the day while slowly increasing the time that they are in the crate each time.  

Here's a couple of other things to consider:
1) Say the same word each time you put them in the crate and they will eventually learn to go to their crate on command.
2) While they are young, you should block off any extra room in the crate to keep them from eliminating in one area of the crate and hanging out in another part of the crate.
3) Don't use the crate to punish your pups - the crate should be a safe haven for them and they should only have positive experiences with it.  This way, they will learn that the crate is their safe space, their own little den.
4) Young puppies can not hold their "need" very long so don't leave them in the crate for long periods.  Regardless, you should put down some newspaper to make for easier cleaning in case they use the bathroom in their crate.  The crate will help tremendously in housebreaking your pups, but it does take some time.