Shaping is likely what you want to use.
What can be done will depend on your equipment.
You might shape all to 5 Mbps and provide each remote a minimum of 25% of the 5 Mbps.
e.g.
ip extended access-list remotesite# (1..4)
permit ip #.#.#.# 0.0.0.255 any
permit ip any #.#.#.# 0.0.0.255
class-map match-all remotesite#
match access-group remotesite#
policy-map 5Mbps
class class-default
shape average 5000000
service-policy remotes
policy-map remotes
class remotesite#
bandwidth percent remaining 25
interface (to HQ or remotes)
service-policy output 5Mbps
[edit]
Beside equipment limitations, unclear what equipment sits on the LAN segment in the center of your diagram. If you only have routers as shown on your diagram, you might modify the above for the HQ router outbound. Remote sites, if you also need to regulate inbound bandwidth (to HQ), is a different problem since you can not easily coordinate bandwidth usage between them.