Hey dude, you have a band to back you - and they all probably started right where you are. Go for it! They are all encouraging you, which means that if you make a mistake (and you probably will - who cares?) they will pick you up. They'll keep on going and you can jump in when you're back on top of things again. You say you do not want to perform often, but this is in front of an audience that will be in your corner instead of out to get you. I really think you have an ideal situation here. Just play for yourself - the other guys in the band are there for decoration and the audience doesn't exist. Once you feel the band carry you along I think your opinion will change - maybe not about the perform every week kind of thing, but I bet you will love the daylights out of your first gig! Break a leg!