How many branches do they have ? If it is more than 16 then you may face scalability issue in that design. With 3850 as MC you can have max of 16 MA. Refer page 30 of the given presentation for scalability matrix.
BRKCRS-2888 - Converged Access Design Options
I would configure each site 3650 as MC/MA with required AP licence. In that way all your branch communication will happen within branch without any dependancy on their HQ MC. If you require services like Guest WLAN across the sites, then consider to have a Anchor WLC at their HQ. 3850 cannot be used for that functionality. It can be either 5760/5508.
Here is some other useful references for CA design.
https://supportforums.cisco.com/thread/2249117
HTH
Rasika
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