We don't have our kids in the Boulder Valley School District but it has a reputation for meager gifted services. You may want to contact Boulder Valley Gifted and Talented to see if they have more current info about options: www.bvgt.org
On their website they mention that Macintosh Academy (private school) is trying to open a Boulder campus. Peak to Peak Charter school has a good rep for serving a diverse population well.

You may want to consider neighboring counties. Adams County has two gifted charter schools that I know of Stargate and Westgate but it may be difficult to get your kids in depending upon age. I seem to recall that when we looked at them that they tended to be hard to get into for the lower grades but had more openings at the upper grades. You also could consider Jeffco. They have gt center programs scattered throughout their district in neighborhood schools. You may want to call the district gt folks and talk to them about realistic options.