We have multiple hounds, but I've always wanted a Newfie, so I have some thoughts for you

1. Agreeing with poster above about possibly not spay/neutering until later, I would get a female. If your hound is not neutered or was neutered "late", he may not take well to a teenage male intact Newfie. Our female hounds get along fine, but our males, if neutered after their first year, will still once in a while take each other on.
2. Talk to breeders about differences in coat types between sexes and colors. I'm not expert, but it seems as though female Landseers (the b+w ones) tend to be slightly less coated than say the black males.
3. Also research breeders whose Newfs have "working" titles. This shows stability of temperament, willness to please, and not just emphasis on size and coat.
4. Take seriously the coat issue. You may have to have him/her professionally groomed on a regular basis if you are not able to commit to the time. Mats HURT a dog, especially when they're tight to the skin.
5. Consider a dog older than a puppy, for the sake of your older dog and your children. Some reputable breeders have "returns" or former show dogs to place that might fit beautifully into your home without you having to go through the "puppy terrors". If you do get a pup, be sure to crate train it, and have a place where the older dog can escape to.
6. Just me, but I'll be buying pet insurance when I finally get my Newf. Even with all the health clearances in the world, they are a giant breed, with some serious possible health issues.
It doesn't sound as though you've met any in person yet. Please consider setting up appointments for a meet and greet with a few different breeders, even if they don't have pups available at this time. I LOVE Newfs, always have and always will, but, like any breed they're not for everyone.
Good luck!
Terri