I think (haven't been for ages) that something like vegetables in tomato sauce would be low syn.
The trouble with tapas is it's mainly fried as it's quick cook stuff.
If it was me, I'd go out, enjoy myself, then get back on plan the next morning. I did that last weekend, and cut down my syns for the week, and still managed to lose 3lbs. Just goes to show you can do it!