<<"What do u mean by 4,5,6,&7 have slack time please give some more idea.">>
The days as you wrote them are not full. So you can take some time for leisurely exploring or relaxing. Or spend more time at the places mentioned. Of those days, Day 6 is the most full, and can still have time to wander in Luzern. Or, you can pick a slower route to Pilatus.....boat to Alpnachstad, then cograil.....
Any of the places that you mention could be nice for a relaxed day or two (as noted in item 5 - "just relaxing") ; my own preference would be for Luzern.
Take a train to Flüelen at the southern tip of the lake, and ride a lake boat back to Luzern...3 or 4 hours. Maybe get off and explore a town and catch the next boat...typically one hour later.)
Zürich is particularly nice for walking through the parks along either lake shore. I like to take a train or tram/bus to Station Tiefenbrunnen, then walk back through the parks to town.
The Jungfrau Region-
<<"Also, my son read about Grindlewald so do u suggest we change our base from Lucerne to some other base near Grindlewald. ">>
My advice is to read further - here:
Note the comments about each village on the right...scroll down..
Grindelwald has nice stuff nearby (First, Pfingstegg), but my own personal opinion is that it is excessively commercial, with a long string of restaurants, shops and hotels with pleasant views toward the Alps and the Männlichen prominence.
Children may not care for charm, but I find the other villages more appealing.