I was actually just re-reading this stuff the other day, so I figure I'll chime in again.
First, of course Adam & Eve had daughters -- otherwise there wouldn't have been any grandchildren and the race wouldda died out right there.
Yeah, incest, icky -- my husband says that they all had "clean" DNA at the time, so inbreeding wasn't yet a problem. Only two of their sons are named but that doesn't mean they didn't have lots of other kids.
Second, it doesn't actually say if they had any kids when they were kicked out of the Garden -- the assumption is that they didn't, since none are mentioned, but then, when God was telling them the consequences of sin, he told Eve he would "greatly multiply" her pain in childbirth, which
could indicate that she'd already been through childbirth at least once.
PJ