The author has MS, so her husband steps in for her and takes their kids on roller coasters and field trips.Courtesy of Lindsay KarpI had a vision of what motherhood would look like for me, and that all changed with my MS diagnosis.I can't go on long hikes or ride roller coasters with my kids, but my husband steps in. I'm glad he's doing the things with our kids that I can't.I always thought I'd be a fun mom; the mom who plans class parties, expl…