In this situation, I would not use VLANs at all on the SRX end. It sounds from your description that the goal is to use a single port on the SRX and "virtualize" that into a handful of distinct virtual ports. For this I would recommend using VLAN-tagged sub-interfaces. The distinction is that VLANs are a layer-2 construct that would allow you to both identify traffic traversing a shared-port, but also to share that same broadcast-domain across multiple ports. In contrast, a VLAN-tagged port with multiple sub-interfaces is a layer-3 construct, only using the VLAN-tags for the identification of distinct traffic-flows
Creating a vlan-tagged sub-interface is particularly simple:
set interfaces ge-0/0/1 vlan-tagging
set interfaces ge-0/0/1 unit 100 vlan-id 100
set interfaces ge-0/0/1 unit 100 family inet address x.x.x.x/24
set interfaces ge-0/0/1 unit 200 vlan-id 200
set interfaces ge-0/0/1 unit 200 family inet address y.y.y.y/24
The EX side can remain as a trunk port with multiple VLANs (as is most common), although it is interesting to note that EX switches can support vlan-tagged sub-interfaces as well.
Ron