Just...don't kill them. Play with them for a while, and they'll begin to trust you to defend them. I do suggest taking a somewhat overprotective role at the outset, then just help them ease into their niches in the group. If they're squishy then you probably mean spell casters or a rogue. If that's the case, make it clear that, in a direct fight between you and them, you're supposed to win. If they think you're much stronger then them with no idea that you're supposed to be so, then naturally they'll be on edge. Some specific classes would be good to know though, so please provide them if you would. If this is your first campaign together, then once this campaign is over, assuming you haven't done something horrible, they will probably take your optimization fairly good naturedly from then on. I actually suggest making this a fairly short campaign, if it's your first time working with them. Make this campaign an acclimation period. From an actual game perspective, I very much suggest that you get some protection against control type spells. You know the type:charm, domination, just mind control spells generally. If you're that confident you could beat them all in a fight, and the GM knows this, then if they're a good GM they'll likely try to control you and turn you against the party at some point.