Actually, 2 guitars are the best thing you can have in a band ONLY if they are tuned and set-up good. One of them as a rhythm guitar, and the other ona as a solo guitar, so none of them plays the same thing.
I'm in a band of 8 (drums, bass, solo guitar, rhythm guitar, keyboards, vocal + 2 girls as lead/back vocals), and the sound is very rich and full...
About keyboards in a rock band... well i think the first thing you have to learn
is improvise... and A LOT. 2 main sound to use would be a piano and an organ/hammond sound.
The problem is those 2 are played in a total different way. When playing the piano you'll be using both of your hands most of the time with some sort of blues patterns and fill-ins (very often), and the hammond will mostly play some fifth-power chords (i don't know how to call them properly so sorry

) with a bunch of sliding and licking similar to piano blues fill-ins.
Leslie comes great as well.
I don't want to spoil it for you but 6 months of playing the keyboard just won't do any good to a ambitious rock band. Just keep on practicing, and in a short while when you get the hang of it you'll know what I was talking about.
First you'll reach a "fear of soloing". You start a solo and when you make a mistake you stop - a BIG "no-no".
The key to get over that is to stop thinking of what you're going to play, and just play... Don't mind the mistakes at all... after a while, when you "set yourself free" you'll correct the mistakes. After that is just plain practice and experience.
Good luck