Delaney has grown on me a lot as of late, and I think the NN Laney would be very cute. Overall, I favor Laine much more, but Delaney has the same feel imo. Erin isn't ordinarily my style, but I can definitely understand why you'd want to use it. I think the combo is very nice, and using Erin is a lovely gesture toward your sister.
Some boys' names that I think go well with Delaney:
Austin
Aidan
Brendan
Conner
Cade
Caden
Cooper
Camden
Cameron
Dylan
Deacon
Evan
Grant
Ian
Jordan
Kyle
Kevin
Landon
Liam
Nicholas
Owen
Parker
Preston
Quentin
Roman
Ryan
Spencer
Trevor
Trent
Travis
Wyatt
Weston
Zachary
Jennifer Nicole
...Loving the Names...
Ariella Faith, Elisabeth Maria, Olivia Jasmine
Cade Preston, Grant Joseph, Jude Hamilton