Hi J. - all 3 of our kids have had this...it lasts about 3-7 days. Our doctor told us to mix 3 cc of Children's Tylenol, 3 cc of Children's Benadryl and 3 cc of liquid Maalox, and give the mixture up to 4x a day. On top of this, I also gave Motrin every 6 hours to keep the fever down. It did help alot.
Re: flying...this unfortunately is a very contagious infection. I know it's hard to miss something so important...and I also know what's like to fly a 5 hour red-eye with a sick child. It's miserable. The concern here is this is a major virus (also can cause Hand-Foot-Mouth Disease) which is miserable for a child to have to endure.
I would wait until the day before you are supposed to leave and see how you guys are...and see your doctor to get his/her advice on whether or not you should travel. If not, you can get a note from your doctor and give it to the airline...they will postpone your trip if medically necessary (we've also had to do this and the airlines usually work with you)...
Perhaps you can just fly out a day or two later when the infection, and fever, are gone....that way you both feel better and no one else around you is at risk of getting this.
Good luck to you both - hope you feel better soon.