After exploring caves in Phong Nha it's hard to be impressed! It's a nice cave though, you'll need a torch as there's no light and you can explore further.
Beautiful cave, some stalactytes are impressively massive. You can explore just first 1km where the path is built or if you pay much more you can go deeper into the darkness with a guide. That would be a great thing to do there!
I was there mid March and there were locals scattered around paying respects in the cave. It had very authentic vibe. Many Buddha statues, tiger paw footprint, colorful fabrics.
Our favorite family cave. Pretty short hike not too intense my kids can make it ok. So fun to go through the cave though and see how beautiful and incredible this earth is! Our favorite tour, totally worth it.
It's best to get your tickets for the tour online. That way you can be sure what time you are getting and plan accordingly. If you are concerned about the hike, get there a little early and take your time.