The area of Keystone/Breckenridge gives you the option to head to Arapahoe Basin if you need better snow (they stay open really late season).
We always go mid March, so I don't know about late March. Steamboat was always fine then, but we went to Beaver Creek last year (and going this year) and maybe it's a bit better. It's pricier though. Steamboat is also at least 2x the drive time (we fly in, but my brother lives in Denver and he will come join us for a night in Beaver Creek but Steamboat was too far).
Mama to my boys (04,07,11)