For constantly having treats floating around the house in copious amounts for training, our dogs rarely get treats just for treats.
Kobi gets so many treats within the day as part of his training efforts that I never feel that he needs treats for treats. When he does get a treat it's usually a long lasting bone to keep him occupied for a little while.
The trick with treats at our house is making sure there is a fair balance, which I usually fail at. If I'm training at home with Kobi, he'll be getting a pile of treats while poor Scout just looks on longingly. But if they are getting a large treat we make sure to give them each one of the same thing to ensure fairness and no fighting. Recently I discovered that Kobi goes crazy for carrots which is a blessing because I can now give him a full carrot in the place of a bone and because Kobi is such a slow chewer it takes him almost as long to eat the carrot as it takes him to eat a bone.
Now that being said, Kobi must preform a task to get a treat, whether he's training or I'm giving him a bone, he has to work for it, and the bigger the treat, the harder he has to work (multiple commands in a row), where as Scout on the other hand, just gets the treat. He's worked hard over the years we've had him and preformed trick after trick when on his Therapy Dog visits, Scout is a retired dog.
When we did do Therapy Dog visits low calorie treats were a must for us. Some volunteers have tried to not allow their dogs any treats during visits to avoid a growing waistline, but I personally found that people would get disappointed when told that they couldn't give your dog a treat.
When I was doing my visits with Scout I had gotten into making treats and at the time low calorie dog treats weren't really in demand. So we found two types of treats that worked for us, they weren't the healthiest of treats, but they were the perfect size and were low in calories, meaning Scout could eat a pile of them on his visits, skip a little food at dinner then still be on track.
When visiting we used primarily Good Bites dog treats, they were small mini shaped bones (and sadly the look of the treat when doing therapy dog visits is important to, people like the idea of giving a dog a bone, even if it's a miniature bone.) We would also use the Temptation Cat treats as a last resort when we couldn't find the Good Bite treats.
The only problem that arose from using these small treats was having to prove to people that Scout wouldn't munch their fingers off when presenting him with a treat and having to show kids in particular, how to give a treat in the palm of their hand if they were nervous that Scout would nip their fingers. Scout was always a gentlemen and never lunged at treats, he would gently take the end sticking out from your fingers and wait for you to release the treat before practically swallowing it whole.
Now that I've started making my own treats I'm hoping to make some treats that are just for treats. As Kobi progresses in his training he requires fewer and fewer treats on daily activities such as walks, leaving room to give him a couple more just because. And Scout, he'll continue to get treats just because.