Juniper Beach is nice and the fishing is good, but if your wife loves good fishing than she will put up with the trains.(They go by all day and night) If she is like mine after the first night you are in trouble, or moving. There is a nice swimming hole for the kids at juniper as long as the water level is not to low.
You might want to think about going to barnes or williard lake rec area and driving to the river for fishing above ashcroft.
I have not stayed at the lake rec area but have had friends stay there, I do not know how good the camping is there so i would ask first.
My friends that have stayed there don't have kids and said it was ok. They stay there to avoid the trains.
I have a drift boat and camp along the river, ear plugs and lots of beer is needed for a good night sleep, as there are trains on both sides.
Good luck.
Bring lots of dry stoneflies with golden and green bellies 1"-1 1/2"