I think it's better to include "Citizenship Grants" or "GRANTS ADULTS" as the second line whether it's regular or priority mail, it might help in quick mail sorting.Regular mail will be much delayed. You might want to use Xpresspost service of Canada Post and send it to following courier address:
CPC-Sydney
49 Dorchester Street
Sydney, NS
B1P 5Z2
Eventhough CP xpresspost suffering from delays as well, I highly suggest you should use Purolator or Fedex to ensure delivery in 1-2 days by dispatching to same above courier address. Good luck!