Continue fighting to see those kids. I understand how difficult it must be to try and juggle both the households, but you need to let your kids know you do care and love them - even if she is interfering with your time with them. The day will come they will grow up and see the world with a little more maturity and you will want them remembering how much you love them and wanted to be with them.
Having our children hold the same name seems like such an important link, but really, it's just a legal word to help identify us. Our last name does not determine the type of person we will be. Pick your battles very carefully.