I can tell you that before our WDW trips I am extremely careful about not putting us at risk of getting sick if we can at all avoid it! Once I had a friend who wanted to bring her daughter over to play with my daughter so she could go to the gym and get a manicure. I said okay, we were leaving the next day and I was busy but whatever. As she is dropping her daughter off, she mentions the kid was up all night vomiting but is fine now. I told her, sorry but you can't leave her, we can't get exposed. She was really angry! She told me how paranoid I was being but I explained that we had this trip planned for almost a year and no way was I chancing it. I felt awful since this little girl and mine had looked forward to playing but I held firm. So she took her daughter to her sister in law's instead (sil is also a friend of mine) and guess what, that whole family came down with the bug, including their baby and they had it for days. If I had let her drop that kid off we probably would have been too ill to fly out the next day. To the OP, you are not being selfish, you are being realistic, there is nothing more contagious than stomach flu. Good luck!