Coloring hair?

I've had the same hair color/style for almost 2 years. Long, brown, thin, lifeless. I have a school reunion (not was a tiny private school) coming up in a week and I want to do something different to look nice. I was thinking cutting to just below the shoulders and dying the ends (to about ear level, well away from roots) blonde.
Do you think dying, but staying clear of the roots, would be safe? I'm 19w now and we've tried to conceive a sticky baby for 10 years with only 2 early miscarriages and a stillborn daughter to show for it until now. I recently had abdominal surgery to make sure we don't lose this one to incompetent cervix. So I'm trying to be a little overly cautious to do everything right to keep this one alive and safe!