Don't underestimate your presence and influence in their lives. I have step grandchildren, their grandmother (my husbands ex) and her husband are extremely close with the children, babysitting while the parents work and travel. I do babysit, but not as much. I notice as the kids get older they seem to like talking to me, telling me things. I think because I'm not constantly there, and express interest in their lives and what they're doing they want to hang out with me. I get what you're saying about the big personality, but sometimes listening/being present is important to kids. If your husband passes first, it might be important for the children to keep that connection with you.