I am wondering the same thing. My youngest child will be four months past 7 yrs. old when we go next January. He is already 46 inches so he's tall enough right now. Last time we went to WDW, he was 2, so he's never really ridden any big rides. He's ridden some small coasters at an amusement park here in Michigan and loved them. He really wants to try the big coasters at WDW (even RnR and EE), but I guess I'm just afraid of them scaring him. Although, my gut tells me he'll do fine.
Just how intense are these rides? We didn't even do RnR or ToT when we were there last time because our kids were just too small. Hubby and I can't wait to focus more on the "big" kid rides. Although daughter who will be 9 at the time says she doesn't want to to try any of these. I think she's afraid she'll get on it, feel sick or afraid, and then she's stuck on them until the bitter end. She's bound and determined not to try any of the "big" kid rides. We're not quite sure how to handle this scenario either.
Please definitely answer the original posters question first, but then feel free to add comments to help answer my questions about DS and DD too. Thanks so much. I love the DIS boards!!!