about goku's mother..well..when i saw that scene from the movie it seemd like the sayains life style was all about sex,drinks and violence..
its when bardock went to warn the sayains about freeza's betrayal..they showed the sayains in a bar doing what they thinks its "FUN".
where i am getting at is goku's mom could be just a ..ehm..a prostitute
so probably the creators just didn't want goku's fans to think that his mom is a just one night stand..if you know what i mean lol..