IP Wireless Cameras - Overwhelmed Network

My first wireless camera installation may need 20 wireless ip security cameras- though I'm not sure wireless 802.11g is going to be strong enough to carry so many cameras with video (mpeg4). I've got 8 staic ips and use port forwarding for remote viewing. I've deployed 5 Vivotek cameras on the wireless lan with wan capabilites for 10 users (unicast). The office network is currently installed on the same network and consists of 3 wirelessly connected computers (office needs to be separated on another network I believe). I hard-wired the security monitoring computer directly into a Dlink wbl 2310 router, and performance increased, as all 5 cameras are visible most of the time now. I did cut bandwith with low frame-rates and mpeg4 compression to 64Kbs...Security cams should be dependable and these lan feeds are irregular. A site survey revealed other weak wireless signals in the area and I tried to keep conflicting channels away from them. I put a 500 mw amplifier on the router, with an omni directional 9dbantenna on a 10 foot rpsma pigtail and placed it on a short mast outside of the office trailer (during the construction phase of the hurricane rebuild that is underway)...I've had problems with the network fading out and have been told by Vivotek that the maximum useable cameras for a single ap is probably 5. I can clean up the office by hard-wiring the other 3 computers into the dsl modem (get them off the wireless Dlink)- this should help with reliablilty so I can begin recording events with the 5 camras online now. How to get more cameras deployed is my problem.

I'm having trouble designing the complete network plan. Should I use as many as 4 aps in this overall design plan? Though very difficult because of construction, a better scenario is to run cabling from a camera-to-switch-to-router (for as many of the cameras as possible). For now, if I deploy multiple aps, don't they have to be on separate channels to keep from interferring with each other?

A newly incorporated location, across the street from the main office, has installed a new dsl line and I have purchased an Engenious 3500 bridge/ router - I need to join the 2 networks. This network scenario (building construction was completed) can be deployed with hard-wired cameras that broadcast wirelessly through a camera-to-switch-to-wireless bridge. A similar antenna configuration for the ap/ bridge outside the building is planned. The ap/ bridge is wireless but this model requires hardwiring into the network to transmit wirelessly. Since the device will be on another network across the street from the main surveillance computer/ dvr, do I need to use bridge or access point mode ? I'm thinking bridge...I was advised to use a separate surveillance monitor for the other network. This challenging project is difficult since I'm relatively new to network construction. This site looks like a good one for some advice on planning the completed network. Anything helpful would be welcomed. This whole project has been seat-of-the pants, since my experience is limited...Thanks. Topo of the construction location is visible: realpanoramas.com/upload/?folder=content...figfile=config10.ini