Defendant is under indictment for penetration of child's sexual organ with his tongue. Defendant's custodial statement denies penetration but admits to mouth/genital contact by him on victim.
May I add this different "manner or means" as a second count to his pending indictment through a 28.10 motion
Or should I just go to trial and -- if victim persists in telling me that there was no penetration -- seek a jury instruction on that unpled "manner" of committing the same offense?

The better practice would be to re-indict with a second count. Of course, as you argue, the addition could be nothing more than an alternative way of describing the conduct already charged. There is no clear answer on how an appellate court would deal with that issue.

With sufficient time, I would always counsel reindictment in this situation. Why create an appellate issue? If time and/or circumstances don't permit, you might want to use your fallback plan.

why even try a fact issue of penetration of sexual organ with tongue at all? it's still agg sex assault for sexual organ of child to contact mouth of defendant.

child sexual abuse cases are hard enough. don't make your burden higher than necessary.

so my .02 is to re-indict with on first degree felony agg sex aslt alleging sexual organ to mouth contact