The children of Vegeta and Goku marrying would preserve the gene longer but eventually the end result will be the same. All of Goku's children were stronger than he was at their ages though. I don't buy that either, a saiyan is a saiyan so females should be able to do it.
I hold out the hope that the saiyan gene altered the human ones making every descendant more like Gohan. Gohan was the only one to be born with a tail but the power he had far exceeded any saiyan and his most powerful state is his base one.
Goten too was seemingly born able to go super saiyan but no known tail.
I think the genes mix in odd ways but it all ends with the child be stronger than the saiyan parent was initially. If that trend continues I'd say that all of Goku's human descendants will be strong though they may lose access to transformations since the saiyan gene is to deluded. However if their all like gohan they won't need them.