Hi x10sandy and welcome to the community.
The problem I see with your setup is going to be range. You say the drive is 300 long. Is the gate at the end of the drive out of sight from the house? My thoughts on a cam are if you can see the gate from somewhere in the house you may be able to go with one of the cams that has a zoom. This would allow you to see who's at the gate from a distance and perhaps overcome the transmission range problem for the video. The other possibility is that a cam with zoom could be placed elswhere on the property to see the gate and still be able to get the RF to the house. The motion sensor issue for a light might work using the X10 floodlight unit PR511 (http://www.x10.com/products/x10_pr511.htm)
I don't have a PR511 but if you do a search on the boards here you will find information on it and some of the issues others have had.
(http://www.bdshost.com/X10/lpup.gif)---(http://www.bdshost.com/X10/lpup.gif)---(http://www.bdshost.com/X10/lpup.gif)---(http://www.bdshost.com/X10/lpup.gif)---(http://www.bdshost.com/X10/lpup.gif)---(http://www.bdshost.com/X10/lpup.gif)---- K D R