Well, I'll help you out a little bit, Steve...
St. John came onto the Project near the end of the 7th Virtual Season as a replacement for Gooshie ("I'm Not Sure You'd Understand, Old Fruit" immediately following "Fallen Hero Parts 1 & 2"); and Stephen was introduced during the first half of the 8th Season as the son of Sam and Donna. Sam leaped into himself on the day before he stepped into the accelerator in 1995, was reunited with Donna, and Stephen was born 9 months later ("I Will Love You Forever Parts 1 & 2"), which would now make him about 8 or 9 I believe, since the current date is supposed to be 2004. The Season Summaries at the TVS site mention all of the important plotlines that have taken place over the past 4 seasons.
On a side note, about the TEA thing... as far as Sammy Jo is concerned, many of us would place Melora Hardin in the role, since she played Abigail, and because the girl who played Sammy Jo as a child also played Abigail as a child. Same goes for Edward St. John VI, I think. At least, I imagine the late great Roddy McDowell in the role since he also played his father in "A Leap for Lisa". But MJ would be the final word on that, since I believe it is she, AJ and a few others who "cast" the roles of all the recurring characters in TVS and QR, such as Sammy Jo, St. John, Stephen, Tala, Siren, Lothos, Ziggy, etc. (Not sure about the Calavicci girls though.) However, everyone's entitled to their own opinions on who would play whom, so go for it, Steve.
P.S. By the way, good story, AJ! Well done!
P.P.S. When my story comes up in January, I can tell you right now that I already have an actor picked out for the new character I'm introducing.