You might one to consider the following points from my experience with my A60.
I've tried taking fireworks last year with my A60 and the fireworks turned out blur even when i use a tripod(not a sturdy one though).
One conclusion i made is my tripod is not sturdy enough, hence when i depress the shutter, the camera together with the tripod tends to 'sink down' too. i tried to press lightly but it still happen so my advice is to get a STURDY tripod. If even after getting a STURDY tripod but u still get blury pics, i guess thats the limitation of our camera(A60/70) since there is no means we can use a remote trigger.
One possible solution is to use the 2sec self timer but you'll have problems catching the 'bursts' of the fireworks as it's really difficult to estimate.