Ask Mr. Smarty Plants

Viburnum suspensum (viburnum) is a non-native shrub that was introduced to North America from Okinawa and other islands of the Japanese Ryuku Islands.  I found one commercial nursery website, easyBloom.com, that had this to say about Viburnum suspensum:  "The fruits are toxic and can cause stomach discomfort upon consumption."  The Canadian Poisonous Plants Information System lists another viburnum, Viburnum opulus, that is considered mildly toxic.  However, the following toxic databases do not list any viburnums at all.

Cornell University Plants Poisonous to Livestock

University of Pennsylvania Poisonous Plants

Toxic Plants of Texas

Poisonous Plants and Mushrooms of North Carolina

The ASPCA's Toxic and Non-Toxic Plant List – Dogs under "Plants Non-Toxic to Dogs" lists blackhaw or sweet viburnum (Viburnum lentago) as being safe, no viburnum species are listed under "Plants Toxic to Dogs".

So, the berries may or may not be mildly toxic to your dog, but there aren't any reports of leaves being a problem. Addtionally, there doesn't seem to be any indication that the berries could be deadly. Perhaps your best bet, if you want to keep the shrub in the yard with your dog, is to cut off the fruit clusters and dispose of them as soon as they form after the tree has bloomed.

Alternatively, perhaps you could consider replacing the sandankwa viburnum with one of the viburnums that are native to Texas.  There are 6 species of native Texas viburnums and none of them are on any toxic plant list that I could find. The Texas viburnums are:  Viburnum acerifolium (Mapleleaf viburnum), Viburnum dentatum (Southern arrowwood), Viburnum nudum (Possumhaw viburnum), Viburnum prunifolium (Blackhaw), Viburnum rafinesquianum (Downy arrowwood) and Viburnum rufidulum (Rusty blackhaw viburnum).