If as you say much of your families wealth is in exxon I would consider some diversification.  Exxon will do well, but as you said eventually angry americans who are sick of $4, 5, 6 gas will come for their head (and their profits) even though they have nothing to do with the problem.  These types of actions of course are counter productive as they reduce the money avaliable for reinvestment into energy infrastructure. 

The other problem with Exxon, Shell, Bp, Chevron..ect. is that they are now way too big to replace their reserves.  They can't be bothered to go after the small bits of oil that remain so they are in effect in the process of liquidating their asset base.  You are much better off investing in mid-ter exploration/produciton companies that can capitalize on the smaller average size of discoveries.