SFGAm hasn't been my home park in many years, but American Eagle is the furthest ride from the entrance besides perhaps Goliath. No need to run to get on it. It is far less popular than many of the other coasters, plus being at the back of the park will make the line build slowly. If you do want to hit Little Dipper, I'd hit it on your way to the back (I'm not sure how many trains they run as they built it after I left). The Jr. Vekoma is in the kiddie area that, if they are enforcing the rules, you won't be let in without a kid. Unless they changes this rule, but I did check it last summer when I was there and this was still the case.
So don't put off American Eagle until the end of the day, but no need to run. My two cents.