Hi there! Well the diet sounds okay. I would not feed the finches/canaries though, espeically if you are unaware of how they died......disease, etc. Make sure you are usually a vit.D3 calcium supplement. Also you could be right regarding the live mice.........this is one of 3 reasons I do not feed live prey to them. They can bite, scratch the tegus mouths pretty, or have a tendency to lodge in their esophagus. Pam brought up a good point regarding MBD, though tegus are not prone to this. They seem to resist MBD more easily than other reptiles. It's not impossible, just difficult if they are getting ample vit. and mins as required.
Greg