I think it is a nice thing to offer, but I can see it being a lot more trouble for you than it's worth, because like others have said, personal preference is almost more important than product quality for what makes one brush ideal for one person and horrible for another. The same with ear-tipping supplies, given the myriad of different styles that people favor (some swear by the Japanese tape, others by glue alone, etc). People are equally opinionated about the types of toys and treats they give their pets. I think you'd be hard-pressed to find a kit (be it grooming, ear-tipping or toy) that would have universal appeal for all (or even most) breeders, let alone their eventual customers. I think that you'd have to offer SO MANY different options and customizations for breeders to pick and choose from, it would be a logistical nightmare for you.
As a first-time puppy owner, I'm not sure I'd want a pre-made grooming (or even toy, probably) package from a breeder. I would appreciate the gesture, but I like to pick and choose what I buy, and only buy what I actually think I will want/need, usually after I've researched my options and considered several possibilities. And remember, not all pet owners plan to groom their dogs themselves. Personally, I am perfectly comfortable bathing and brushing my dog, but I get nervous about the idea of cutting the hair, because I don't know what the heck I'm doing and would rather leave that to somebody who does! So a grooming kit with scissors would be wasted on me!
I also liked Chris's idea of hosting puppy showers. I know that some people would just eat that up. I can say that personally I would not have wanted a puppy shower for our puppy, and I'd feel weird going to a shower for a puppy. We love our dog. He means the world to us. But we definitely don't consider him our baby.

So, for someone like me, you could also offer a plain registry, without the party, where people could just make wishlists of what items they want. Before we got our puppy, I actually did something like this. My mother-in-law was an assistant manager at Petsmart at the time, and she offered to buy us some supplies (like a crate, bowls, etc.) so that we'd have everything in place for the puppy (and get her employee discount, whee!) but she wanted to be sure we got stuff we actually wanted, so I made a wishlist on petsmart.com and emailed it to her, and she was able to buy the items in her store. I know that this option would really appeal to people, especially if they could do it in-store so that they could actually see and touch the items before putting them on a list. For instance, my MIL didn't get us the crate we asked for, because she said it wasn't actually as nice as one of the other varieties. We would have known that if we could have seen them in the store before putting them on the list.
Perhaps you could just offer a discount card for breeders, or you could sell them little coupon books or gift cards to give to people with their puppies, instead of a gift basket. I would have been happy to get a gift card, because that would still let me pick and choose what to use it on. And I would rather have a coupon for a free or reduced-price grooming than a pair of scissors and brush I might not like any day!
