Keep in mind, this is comic book time. It hasn't been 23 years for ANY comicbook character since Crisis.
As much as I like the Infinitors, I think ultimately, they were a mistake as it draws attention to the JSA ages. The JSA are linked to WWII and this anchors the kids as well. The dates the JSA had kids would have to be getting pushed further and further back. Unless a Roy Thomas comes along and says someone kidnapped the kids and they were trapped in suspended animation for X-number of years until "recently" restored.
Robin's age, chronologically he should be much older than Helena, but thanks to the Iank Karkull incident, he ages slower. I think he works best as being the same age as the Earth-1 Batman and thus serve as a nice counterpoint to that character.
| > As for Robin's age he should be about 30 years older than Huntress and since there were no dates given in the story I think it is safe to assume that "now" on Earth-2 is not 2008. Some years have passed since the Crisis but not 23 years.|