Hi Sara,
You don't mention why you are considering surgery, but I really hope it is not just based on the measurements. The numbers you mention (30-40) are really not in the surgical range for an adult, unless you are having other issues such as pain that has been refractory to all other treatments. If you are very athletic now, I do not think you will enjoy your new, fused spine unless you are doing surgery strictly to relieve pain. If you are not having significant pain I would strongly recommend deferring surgery at this point, for as long as possible. I am curious why two surgeons recommended surgery for curves of 40 degrees or less, as it is really outside the standard of care.
Gayle, age 50
Oct 2010 fusion T8-sacrum w/ pelvic fixation
Feb 2012 lumbar revision for broken rods @ L2-3-4
Sept 2015 major lumbar A/P revision for broken rods @ L5-S1
mom of Leah, 15 y/o, Diagnosed '08 with 26* T JIS (age 6)
2010 VBS Dr Luhmann Shriners St Louis
2017 curves stable/skeletely mature
also mom of Torrey, 12 y/o son, 16* T, stable