We can only go to Andaman as Nicobar islands are restricted for tourist. if it's a seven day trip
explore the port Blair city and must watch the light show of the central jail..
then book a cruise for Neil island and explore the two famous beaches and the natural coral bridge which also there.
then to Havlock island there are few beaches to explore as well and do the scuba diving there it's more beautiful there.
return to port Blair and then go for the north Andaman.
and if you have days try for viper island as well there is a ferry for that