I think it was mistake in a first place, to end romance from ME2 with sex scene. Even walking without a suit may be deadly for Quarian, not to mention about phisical contact. If Shepard really care about Tali, he would never expected anything like this.
Without phisical love, relationship between Tali and Shepard, would raised to the new level - they don't are closely because they lust each other, and because of this, sex is unecessary. They even can't have children(I hope so). OK, kiss will be good, but nothing more.
Now I don't care if Bioware shows Tali's face, but if the decision would belong to me, I wouldn't show her face, just to piss off this part of fans who MUST know everything, and don't respect any mystery. They moanin' already forced BW to create possibility of having sex with other species in ME2.