Can a conviction for DWI with a child passenger be used to enhance (as an underlying conviction) a defendant who is charged with felony DWI (3rd or more)? I believe it can, but some of the ADAs believe only a standard DWI(i.e. DWI 1st or 2nd) can be used to enhance? Please advise.

Yes, it can. See PC 49.09(c)(1)(A)

I think DWI w/ Child cases that were adjudicated with a straight probation before 9/1/05 cannot be used to enhance. After that date, the legislative fix to effect. (See TDCAA's 2005 Legislative Update Manual p. 13-14)