You are the memory keeper and life collector. Yet there are most likely not that many photos of your kids with you in it (apart from the old selfie). You and them, living life, you know, the normal stuff. Which is what will become the major stuff. The moments that seem so banal right now, but will be treasured later in their life.
So get in the frame and leave evidence behind, that the mum your kids know and love right now actually existed.