Be good to your girls and get them in a good, supportive bra! As long as it fits properly, you should not get clogged ducts. I wore underwire nursing bras with all three bambinos... a total of 42 months of nursing... no problems.
I love this brand:
Bravado Nursing Bras.
If your girls are ladies
just google plus size nursing bras and you can find all sorts of sizes.
I was fortunate that on two separate coasts, I was able to find specialty lingerie shops with expert fitters. One was at a hospital, the other was independent but near a hospital. Besides nursing bras, they also carried things like mastectomy bras and prostheses, so those ladies knew a lot about boobs and what it meant to have a quality, well-fitted bra. Check with your local hospital or breast care center (mammogram/surgical place) -- they may know of something in your area.
Good luck!