Underlining?

I bought some super cute polka dot stretch twill that I would like to use for a secret agent trench for my daughter. I've made this pattern twice before -- once in a ponte knit and once in a lightweight suiting. The knit was very popular but my daughter said the suiting one was too cold. I don't think it was too lightweight but it wasn't cozy enough (she would usually wear a trench over a short sleeved shirt if it was cold enough to need an extra layer but not cold enough for fleece). So . . . I'm thinking of underlining the next one in light flannel. I'm making view B so thinking I'd maybe just line the bodice and the sleeves not the gathered skirt. Is underlining a stretch fabric with a non-stretch fabric a bad idea? I've never underlined something before but I've taken a look at a couple of tutorials (like this one: http://seamstresserin.com/how-to-underline-sewaholics-robson-trench-coat/ which shows how to underline the Robson Trench coat). Is there any reason why it might not work for the secret agent?