What makes you think you know whats good for the band? The other members might think THEY know. Its a vicious cycle.
Is your band going to be playing gigs? And are you planing on trying to get signed? If so then you'll probably have to it down talk to the band members and see where they want the direction of the band to go. See if it matches yours.
If your just going to be doing this as a hobbie, then maybe you could do some of the songs they want.