Bye bye boobs

I found that my kids wanted specific times as well and needed the reassurance that things were routine.  They came in most days (we live a long way from the hospital) even if it was just for a brief time - a couple of times they were picked up from the hospital by friends' parents and taken off for play dates as it was the school holidays.  My girls, in particular, felt the need for contact and we did a lot of emoji-style texting first thing in the morning and at night.  It could be that they were 11 & 12 at the time, or maybe it's a girl thing.  I always included my 15 yo son but not the OTT stuff.  For your niece and nephew, and probably for your kids as well, the situation is even more loaded given the loss of you sister so recently.  You may want to give yourself an out by explaining that sometimes, immediately after surgery you're so tired that having to talk to people is really hard.  From what you've said, your daughter is pretty grounded and as long as she knows not to expect you to look fabulous, she'd probably be okay - it may be more important to her to see you sooner rather than later.