My sister thinks i should keep my baby's umbilical cord stump for our baby album. isn't that overdoing it?

Some people do: Once the cord stump dries up and falls off, it's harmless and some people do keep it for a memento. What to keep in a baby box or album is a very personal decision, and also varies with culture. If keeping the cord stump grosses you out, maybe you'd feel more comfortable with hospital id bands or other non-organic keepsakes. But dried cord stump poses no risk of carrying infections or anything bad.