Baby will only nurse to sleep

My 3.5 month old will only go to sleep on the breast. It works great at night - he nurses for about half an hour, then sleeps about 8 hours straight. But for naps it's a different story. I nurse him on the Boppy, and when he falls asleep if i try to move him he wakes up. At this point he wants to nurse again to go back to sleep. So I end up sitting on the couch with him on the Boppy until he wakes up on his own. This is also creating problems as we are getting more mobile - I will nurse him and then he wakes up and gets upset if try and put him in his stroller or car seat. Any advice is really appreciated. We are going on a vacation with my family soon and I worry we aren't going to be able to do anything with him because of this.