So what BMI should I aim for???

I am 5'4 and have gained to about 103 (been stuck there for quite a while, but that's another story).  I know my BMI is below the recommended (17.7).  What goal is appropriate?  I am a small build if that helps.  I am a mom to three kids and want to be solidly healthy (meaning not teetering on the edge of being underweight).  Thanks!

20.

If you're putting weight back on, you want to be in a safe range that, if a bit drops off again on maintaining, you will not fall back into the underweight range.

Thanks so much!