Hi -
You will find that the 5500 shifter/brake levers are double/triple compatible - i.e. even though they were originally set up on a double they'll shift all three rings of the triple without breaking a sweat. IMPORTANT: This is not true of Ultegra or Dura-Ace shifters - you have to get a specific triple set to shift all three chainrings.
I say go for it, cable the beast up, and let 'er rip!