I'm a 30DD and LOVE Chantelle bras. And many of them are full coverage and modest so would be perfect for your DDs age. I usually get mine from amazon and NWT from eBay.
I have found that getting fitted by a bra fitter is so important with that hard to find size. The standard size calculators just are way off. The measure under and add 5 for band and then find difference between measurement around bust never comes out to the right size. What does is measuring around the area above the bust/under the armpits use this as band size. Then measure around bust and subtract band size to figure out cup size.
Mom to two amazing DDs ('07 & '09) and a fur baby.
Gluten free since Nov '11 after non-celiac gluten sensitive diagnosis. Have had great improvement or total elimination of: migraines, bloating/distention, heartburn, cystic acne, canker sores, bleeding gums, eczema on elbows, dry skin and scalp, muscle cramps, PMS, hair loss, heart palpitations, fatigue. I'm amazed.