I agree with folks saying that really only you can say what is best for you. We all only know what is best for ourselves. You do what you need to do. If you tell your sisters now, maybe be very emphatic with them that right now, you want to just enjoy your bike ride and deal with this when that is finished and ask them to not dwell on it with you before then.

Keep in mind folks, there is no need for marni to tell the family for their own medical well-being, as this is not her first diagnosis (hence the vigilant screening and the tamoxifen she is taking), so her family already knows that there is now a family history.

We will all keep spinning our wheels for you marni, you just tell us how hard you need us to spin! And come here and vent anytime you need to. I find it one of the best things about online/anonymous forums.