What would you do?

Played a $3000 freeroll last night and it was down to the last 15(top 10 paid).I was in tenth with 9000 odd chips and the blinds were 500/1000 and due to rise next hand.
I get A7 suited on the button and its folded round to me.I went all in and got called by the SB who had 26000,he shows 55 and makes trips to knock me out.I wanted to win this tourney and wasn't prepared to limp along hoping to make the money so i think it was the correct decision even though it backfired badly.
What would you have done in this situation?

This was also the 1st time i've had a royal flush and got 3 all ins too!Beautiful.

With your short stack, that's a pretty easy push. SB's call is fine too - if he thinks there's even a small chance you're stealing he's better than a coinflip.