One option may be to use a parameter that allows the user to select the desired pairs (if I am understanding the issue correctly). Create a string parameter that lists the Alumni, Donors and Friends. Then, create a calculated field that would be placed on the view similar to the following:
case [Pick your Type]
when 'Alumni' then sum([Alumni$_LIFETIME TOTAL GIVING])
when 'Donor' then sum([Constituents$_LIFETIME TOTAL GIVING])
when 'Friend' then sum([Lybunts$_LIFETIME TOTAL GIVING])
Hope this helps a bit!