thanks jib71! i had thought of that, but (according to hyperdia at least) this involves:

Kyoto > Osaka, walk to Umeda > Namba Subway, walk to Nankai (leave luggage at the 手荷物預かり所)

I'm not familiar with Osaka (my dim memory from 4 years ago was of a gently weird and crazily attractive lady who owned the house I spent the night in - nope, nothing happened) - so I'm not sure if the walks (Osaka - Umeda, and Namba - Nankai) are a mere hop skip & jump or a more serious hike (with road crossings, long stairs, etc). I hate to sound a wimp, but anything more than escalators or short, well-paved paths (with my lovely parents - my mom really isn't the fastest walker) could easily add a significant chunk of time between getting off the train and depositing luggage. Of course, I do realise Umeda > Namba is a very short 15min ride, and so my concern is mainly with the "walks".

I'd be glad to be corrected - this must give off more than a little whiff of a***-retentiveness, but hopefully all the obsessiveness on my part will give my parents a (deceptively) smooth experience.