There are plenty of shoots throughout northern to central CO. If you are specificly looking for NoCo shoots, Weld County Fish and Wildlife and Great Guns Sporting have plenty throughout the year. Here is a link to all of the shoots in CO this year: http://www.coloradoskeet.com/CSSA-2.aspx
Answering your second question:
No, there isn't ever a shoot where doubles and 12 gauge are held on the same day. Typically, doubles are shot on Fridays and 12 is shot on either Saturdays or Sundays, normally Saturdays. I hope this helps and I look forward to seeing you at some upcoming shoots!