Yes, you are worrying more than you need to.

7Rider and I just participated in a tri relay together (I swam, she biked) and I know we were both nervous, too, even though we knew we wouldn't really have a problem with our events. When you are part of a team it is natural to want to not let the other members down, even if you're not competing for a podium spot.

It's my understanding that the Nations bike course is pretty flat; between that and the adrenaline I'm sure you'll be good without a rest break. And, if you need a rest, take it! Just have fun!