Hello, I do not think you need to tell any body before. Becasue it will be really depends on your baby's need . You can just sit at the back of coach and use a jacket tocover and your husband sit outside. That will be find. I just breastfeed my son in the plane and train. This is all fine.
Why do you feel embarass? Baby needs to drink milk when he/she is hungry, and it is such a natural and good thing to breastfeed your baby! You just need to use a nursing bid to cover your breast so that no one can see it! Also ask your hubby to take the isle seat so that you can hide behind him. No need to tell anyone that you'll be breastfeeding your baby, and I think they'll be paying more attention to the tour guide rather than you breastfeeding your baby! If you have positive thinking in your mind, you won't feel embarass at all !