MCPS doesn't have every special ed program in every school. Many MCPS elementary schools don't even have inclusion options. That being said, MCPS will bus your son to the elementary school that MCPS considers "local" that has the program MCPS for which MCPS determines your son to be eligible and provide transportation to school and to home (but not to early care or from after care). Generally, MCPS will allow siblings to attend the same school and ride the bus together. This may expand your geographic horizons slightly in Montgomery County. You can find which schools have which programs (at least last year's 2015-16 school year) by reviewing the "Schools at a Glance" here:
http://www.montgomeryschoolsmd.org/departments/sharedaccountability/glance/
It's probably easiest to just review the "Entire 2015-2016 Schools at a Glance" pdf. Based on the discussion, the programs you may be most interested in are the "Elementary Home School Model" (inclusion in a general classroom setting with rotating paraeducator support), "Elementary Learning Center" (self-contained classroom with children generally on diploma-track), and "Asperger's Program" (children with ASD at or above grade level academically, but generally with behaviors that interfere with learning in a general education environment). Note that only two elementary schools have the Asperger's Program, so there would likely be a long bus ride for your children (to either Gaithersburg or eastern Silver Spring). There were 11 schools last year with Elementary Learning Centers. And, there were a number of elementary schools with the Elementary Home School Model.
I don't know how FCPS works.