Thanks all!! I think i get the basic picture, here are some summary points.
With a 1 hour travel radius, I estimate I will get a max of 5-6 hours given the need for breaks, food, jet lag issues. Personally my desire is to be more among people and on a high travel ICE route. A small town somewhere in a river valley.
The options i have narrowed to are:
a) Frankfurt walking tour including Sarvana Bhawan. Ms. Jo, i went to your blog through the hyperlink, did not know that there was a Sarvana Bhawan in Frankfurt, my family will kill me if i don't take them there :)
b) Other options I have narrowed down to are Mainz, Weisbaden, Aschaffenburg, and maybe Heidelberg seem like reasonable options. I am no different from a typical tourist and would like to be among people and Heidelburg is really tempting.. as I visited it 1997.
I will probably switch to researching how much time to get through Schengen cross in FRA airport and train times to these destinations, I will have to wait until later this year for winter schedule i suppose.
thanks all if you have any other ideas, please do keep them coming. Couple of interesting links i found in the travel forum, HT Ms. Jo
https://community.ricksteves.com/travel-forum/germany/day-trips-from-frankfurt
https://community.ricksteves.com/travel-forum/trip-reports/day-trips-from-frankfurt-heidelberg
https://community.ricksteves.com/travel-forum/trip-reports/day-trips-from-frankfurt-part-2-budingen