Well, there are points that supports both moves:

1) The game is named 'backgammon'. According to 'official' bg rules, they wouldn't allow me to make the better move for me. So I should move both dice. If I was playing on the 'real' board, I would move both dice without asking.
2. This site rules doesn't deny me moving only one piece. See http://brainking.com/en/GameRules?tp=23 The rules are the same for both players.

Since game rules are allways an agreement of a community, I'll do the move players here agrees. Let's make a vote. Give your vote here ('move both' or 'do what you can') and I'll make the vote winning move. You have one day to vote. I'll make the move ~24 hours from this moment. My or Sharon's vote doesn't count.