Great enthusiasm - but an almost total lack of preparedness, and really poor judgement. If something had gone wrong (really wrong), imagine the amount of effort it would take for a rescue. The one thing they had going was having someone who was somewhat prepared, and had been in the cave before. They were very, very lucky.
I hope they don't give up on caving, though. They should find a local group of cavers to go with and learn from them. Visit some other caves, perhaps...