Hello,
Usually dry stool is not a problem unless they are constipated or having any problems moving their bowels. It can be a reflection of their diet and dog getting increased amount of calcium or bones or on a raw food diet will ofter have a dry almost crumbly stool.
If you make sure everyone is eliminating daily and taking in adequate amounts of water, you should be ok. If you are unsure about their water intake, you can try adding a little water to everyones food to insure it.
I hope this is helpful and please let me know if you have any other questions.
Dog Veterinarian
Over 20 years experience treating dogs and cats