Terribly unrealistic in many ways, but once you accept that as a Hallmark norm and go with the flow, it's fine family fare. Very creative in the changes to Verne's novel. Very strong production values. All the characters were so hale, healthy, and gorgeous. Everyone and everything had a golden glow. Gorgeous look to it! Costumes and settings were elaborate, ocasionally fakey or too modern, but this fare is to appeal to kids and parents, so concessions were obviously made to engage 'em.
The plot got pretty complicated, but that's not necesssarily a bad thing unless you're really not enjoying it. Not everything has to be simple and pared down. It was long and elaborate, but enjoyable. The funniest thing is how everyone seemed to be able to come and go with ease miles to and from the Earth's surface, crossing underground seas, etc.
Bryan Brown is good as a venal fortune-hunter. Treat Williams is a treat in face and form for somebody who must be 50 years old! The older and younger female leads were fine. The Maori-nosed actor did a very fine job, and was another great-looking specimen for his age. The juvenile male who narrated was perhaps the weakest link, but perhaps the script called for him to be non-descript (pun not intended).
The caveat for parents w/kids under 12 or so is that some consensual sex becomes pretty obvious once the party makes the underground village, and you may not want to deal w/that.