Please post a picture of you and your bike! We love to see other people just like us who love to ride their bike.
We welcome EVERYONE here!!! If you ride a bike and love it: you are a serious bike rider. Who cares if you never race? Many here don't. Who cares if you never ride a century? Many here wouldn't consider it- and they are serious riders. I think being a serious cyclist has less to do with the bike you ride (or how many miles) and a lot more to do with how much you love to ride and how it makes you feel.
That being said- I don't ride with the "serious roadies" because they don't have as much fun as I do. I can probably keep up with them, but for me- riding hard and wearing myself out isn't my idea of fun. Riding my bike for miles and miles and still smiling is my idea of fun. Do what makes you happy! And I love that you're doing it for your granddaughter (and for yourself, too). She'll appreciate grandparents that can run circles around her!