Traditionally, that role is taken by the father of the bride, but any significant person can do that. You can even go alone or have two people walking you. The most important thing is that this isn’t a last minute decision and that you have an open dialogue with your family so there aren’t any surprises.
If there are children from a previous marriage, they should be the first ones to know about the engagement. Avoid sharing the news on social networks before telling your parents, grandparents, and closest friends and family.