If your project is about ducklings imprinting, then bringing a goose into the factor is not a good variable. Time would be a better variable that you can track through your project. By time, I mean how much time you spend with them. The ones you tote around with you at school all day and ones you spend X time with a day at home
Another option is hatching your own and also buying some from somewhere else that are already several days old and have had a chance to bond to their other duckling friends first.
Living things can be a difficult thing to do a project like this with as to truly do time correctly, you need a group that all you do is feed, water, tend to their brooder and that could be an issue (or really, let them fend for themselves, but that's just cruel)
Also, with imprinting to you, you need to remove the other variables - like other ducklings.
Before you get too far into your project, I'd sit down and speak with your science teacher to see if they can help you plan it out to see if it really is a good idea to follow through with or if you might want to do a different project.