Years ago, our 2 youngest kids convinced us to let them get a guinea pig. It turned out to be a great choice. Like yours, they were very responsible -- well, reasonably responsible for kids.
We had two dogs and they were totally fine with Miss Tootsy. Note: When we first got her, she was in a small cage from the pet store which we kept first on a small side table in the dining room. Later, we moved the cage to the fireplace hearth in the living room. By this time, the dogs were used to having her around &, although periodically curious, it wasn't any big deal. Eventually, we felt the cage was too small for her and, consequently, too difficult to keep clean. Tootsy's new digs were in an under-the-bed type clear plastic box (obviously, without the lid). It was perfect! Since it was open, she was more accessible to the kids to play with or just stop & pat. Since she was a little pudgy, she could put her front legs up on the edge, but never, over a couple of years, managed to climb out (I think the slippery plastic surface helped with that!). The dogs (one black lab, the second a boxer/shepherd mix) were always very good with her. If she felt they got too close, she'd bite their nose & run into her little house. When we had parties or small children over, we just scooted her cage up to one of the bedrooms to keep her safe.
For cleaning, the girls did a quick scoop once during the middle of the week and a more thorough cleaning/washing of the cage on the weekend. As long as they were good about that, there was no odor.
We had her for almost 8 years. When she passed away she left a hole in our hearts. By the way, my husband was against getting her to start with -- but became her biggest fan. I think guinea pigs area awesome "introductory pets". And, unlike other rodents, they're diurnal for the most part, not nocturnal.
Have fun!