Sam, welcome to mid-life. Sounds like you are approaching it with a rational level head: mourning the losses, but recognizing what is gained. Just think, soon you will have to bike even slower because little sam won't be able to keep up on her little bike, but if you do go slow for her to enjoy it you will spend more hours on the bike than you can imagine (that might still be 3-5 years off, but the time will fly).