Thanks for the ideas, TE. You have brought several concerns/points to my attention and this is why I asked the question.
At this moment, I don't think I like the idea of an electric underground fence at all because of the obvious problems, eg, they don't keep critters out.
I think that my best choice is to take the time to teach my dogs the boundary lines. They are 5 years old and still very trainable. The golden is a timid homebody and she'll stay close by. The lab mix is the most head-strong, intelligent, adventure junkie I've ever owned. I don't mind the repetition that will be required. I've trained them since they were little with several commands and they do well. The lab would probably walk right past the fence even while being shocked. Yes, this would be cruel and I would not subject him to this.
The other homeowners in the new neighborhood all let their dogs run anywhere they please. This really surprised me when we bought the land two years ago. This can lead to problems.

Thanks again!

Barb