Advice for First time rogue
Here's what I've learned playing a rogue (currently rogue 7/Shadowdancer 7):
As others have said, only get into melee if you're pretty sure you can get out of melee before you're killed. If you can't sneak attack, you won't be doing much damage.
Sometimes that means that you won't have much to do during combat. My solution for that is to carry a handy haversack that contains one of everything. That is, every mundane or inexpensive magical item I can get.
"Just a sec, I've got... some chalk!"
"Just a sec, I've got... a golembane scarab!"
"Just a sec, I've got... a Quaal's tree token!"
When we're up against something I can't sneak attack, I start flipping through my equipment list.
Tumble is great for getting into flanking position or playing Gank The Mage.
Outside of combat, you'll have plenty to do because the rogue is the skills master. With your party makeup, your character can be the party face man (if he has any charisma at all). You can be the scout (Hide, Move Silently, Spot, Listen) and deal with locks and traps. Yes, we've found that it is helpful to disable traps rather than setting them off.
Feats: You don't get enough of them. I like Dodge (it's +1 AC about half the time) but if you've got Tumble then Mobility is only good as a pre-req for something else. Spring Attack would be great but I haven't been able to get it yet.
Other classes: I like Shadowdancer. A few levels of fighter is good, but if you've already got two fighters then I'd go for something different.