AFAIK there are no maintained ranges near Larkspur. I worked in the Palmer Lake area for 5 years and never found something nearby. If you want a monitored range there are a few private clubs down in CO Springs, or a number of public ranges in the 'burbs of the Denver area. Otherwise Vader33 is right. You've got Pike National Forest right in your back yard there. Your best access is going to be to head south to Mount Herman Road in Monument, or north to Dakan Road. Either road will require a good 4x4 with lots of ground clearance, and sometimes the roads are closed or simply impassable in the winter or after heavy rains. Mount Herman Road will take you right up into the NF, but Dakan road takes a long winding path through lots of private property before it hits Hidden Valley Road. Turn left (west) on Hidden Valley and that will take you up into the NF. It'll probably be at least a 45 min trip either way.
Be sure to check the rules & regs of the NF though. I believe there are limits as to how far off a public road or marked trail you have to be.
Good luck! Out of curiosity, are you moving to Larkspur from out of state or elsewhere in CO?