Is it worth getting a JR Pass?

Hi, we are 6 people coming to Japan. Our itinerary is as follows
Arrive Osaka KIX
Accommodation near Ashiharabashi station
Travel to Takamatsu, Shinkoku Island
Travel to Tokyo - accommodation near Tobu Tojo Line (Tojo Line)
And then to Narita Airport

We would also plan to do some day trips by train/subway etc in each of these places

Is it worthwhile getting a 2 week JR pass for each of us ?
If so, will it cover all of the day trips also (assuming that they are on the right lines)
Or should we hire a car? (which is big enough for 6 people)
Do we have to nominate them in advance - or can we be flexible?

I'm a bit confused

Thanks
Lisa