I am answering this as a mother of 4 sons who are from 16 yrs old to 26 years old ...and as a public school employee: Relax about having your little one miss a few days of school!!!!!!!!
Over the years, we have occasionally taken our kids out of school for family trips (usually only a few days at a time) and I can assure you their success in school was not in jeopardy because we did. Even when our youngest missed two and a half days of 8th grade for a Disney trip with me, and his math teacher pitched a fit, I had NO REGRETS about my decision. (OK...I have to brag...now as a high school junior, his PSAT score will rank him as a National Merit Scholarship semi-finalist and he is a straight A student so, obviously, he recovered from whatever he missed those few days!!!)
So, go during Spring Break if it works for you but, if not, just go when it suits and know that there are lots of "teachable moments" on family trips (especially with a young child!!!)! My guess is that your child's teacher will be happy to work with you (with advance notice) to help your child catch up on anythiing missed in class. I stand ready for the FLAMES from those of you who think it is an unpardonable sin to take a child out of school for a non-emergency trip!