Robins have trouble clinging to a suet cage, chico, so if you crumble the suet for them, they'll be able to eat it easier. I think everyone and their brother has luck with raisins except hazel--I've never gotten a robin to eat one.
Do you put them on a deck rail or a feeder or on the ground...?
One thing about snow in March is that it doesn't stick around very long...