Recommend your umbrella. I just had my second one turn inside out on me this week. I'm tired of POS umbrellas and want something sturdy but compact that will cover me and the kids on days like today. DD and I literally got soaked going in and out of daycare, the doctor, the grocery store to get her prescription, and it did not put me in a good mood.
Re: Because it's never going to stop raining...
I have a Columbia rain jacket and pants plus boots for myself (and it's awesome, I really stay dry). The kids currently have rain overalls. They are great, breathable, they stay dry and it just goes over their clothes. With rain boots, we are good to go.
And for quick in and outs, I vote oversized jacket too. Or a poncho.
It's perfect for yucky days