Cross breed dogs or the new craze 'designer dogs' are laden with health problems. You can NEVER guarentee their temperament for many reasons.
One reason for this is that they are bred by 'back yard' breeders meaning they are not registered breeders so it is not compulsary to do health checks on the Dam and Sire.
No registered ethical breeder would ever cross breed. A puglier, spoodle, labradoodle are all mutts no matter how cute they are.
If you want a dog that is gentle with children and is also a good guard dog, get in touch with some registered reputable breeders after researching different breeds. They will cost a little more and you may need to wait a while plus they will check you out thoughly to make sure your home is suitable for one of their puppies but they are health tested, microchipped, and vaccinated and healthy.
If you don't want to wait then why not get in touch with the many dog rescue organisations. Their dogs are in foster care and are temperament tested making sure they are suitable with children, other dogs and generally healthy and happy. They also come desexed, microchipped and vaccinated. The rescuers can also point you in the right direction with suitable breeds.
Good luck in your search. There are so many doggies out there just waiting for their loving forever homes.

