It is true that PADI is not a cave training agency and I would agree with other's recomendations to stick with one of the cave diving agencies. However, if you find a instructor you like and he is convenient and a PADI instructor I wouldn't get hung up on that if I were you. The PADI cavern outline is esentially the same as the others and was probably copies from the NSS-CDS. In either case if at some later date you choose to go intro or full the instructor will decide what remediation is required regardless of caver agency. Equipments requirements for cavern are the same as those for open water with the obvious deletion of the snorkel and the addition of two lights and a reel. Many cavern instructors can give the class and issue a bunch of cards like NACD, NSS, IANTD and PADI. All the same class and you get as many cards as you want to buy.
I would tend to be alot more choosy if the goal was full cave but for cavern only just pick a convenient instructor that you like. As far as qualifications, to my knowlege all agencies require caver instructors to be cave divers. World record penetrations and cutting edge exploration are not required experience to teach cavern. In other words don't make the whole thing so complicated just grab an instructor you think is good and go cavern diving.
I would tend to be alot more choosy if the goal was full cave but for cavern only just pick a convenient instructor that you like. As far as qualifications, to my knowlege all agencies require caver instructors to be cave divers. World record penetrations and cutting edge exploration are not required experience to teach cavern. In other words don't make the whole thing so complicated just grab an instructor you think is good and go cavern diving.