What options do I have if I'd like to have my child in Canada and still maintain my US residency?

It is, of course, your right to decide where to give birth to your child. If you expect not to return to the U.S. for over a year, you should consider taking steps to preserve your permanent resident status here (applying for an advance parole is one of such steps but, alone, might not suffice; discussing the issue on an open forum would be unwise, it should be done in your immigration attorney's office) Another matter is the consequences of your decision for your child: if born in the U.S., he/she will be a U.S. citizen by the dint of birth on the U.S. soil - and a citizen of Canada because of your Canadian citizenship. If, however, you give birth in Canada, your child would have only the Canadian citizenship. You would have to file an immigrant petition to obtain a green card for your daughter or son, and take care to not lose it if your child would be spending extended time outside of the U.S. If you become a U.S. citizen sometime before the child's 18th birthday, and if all the conditions will be met, the child will become a U.S. citizen simultaneously with you; otherwise, he/she would have have an option of filing for a naturalization after reaching 21 years of age (and accumulating the requisite 5 years of uninterrupted physical presence in the U.S.)