Staying away doesn't make sense unless you know that one of the things kids of stepfamilies commonly miss is time alone with their biological parent. Think about it. Since you came along they have to share their mom or dad with you and perhaps your kids if you have them. So every once in a while give them some time with their parent. They need that and when they see you are not always competing with them for the parent's time they might just view you as a friend instead of a competitor.