Hi Marina,
You can use the same. But one question when already an internal table has been declared in both cases -Overview and Detailed for report, why don't you use the same internal tables? It would already have data and you can bifurcate it into display and email.
For Overview:
Say internal table ITAB_OVERVIEW will have data,
if display..display it
if email..use for email..
if display and email...use same ITAB_OVERVIEW.
Do the same for Detailed.
You can avoid using extra internal tables that way. Data fetching will be the same in display and email case anyways so use the already existing internal tables.