Thanks for all the help guys.
Lordneg--> Thanks for the link to the other thread. I was looking for either RPG game or miniature system that anyone uses for Joe battles. I wanted to see what works best and why. I am looking up info on all the suggestions made so it may take a while for me to decide which one we will use for the backyard wars.
Scramble--> I never would have thought to use this:
http://en.wikipedia.org/wiki/Cartoon_Action_Hour, but after looking it up it may be the best for my kids/nieces/nephews. My adult RPG'ers and brothers will want something more in line with the old battletech missions we used to run to get them on board. This however, seems to be the most kid friendly. Also, it seems to be not much more complex than the roll for a hit system we now use. I'm gonna give this one a try.
The Mike-->I have tried Gurps and liked it better than D20, but it had flaws in the build system that allowed for unbalances progression. This is just my opinion and I could use it with some reworking to my taste. I'm just trying to see if anyone has worked out a "perfect" system already before I get all the sourcebooks.
Luftshutze--> These are new to me, but Mongoose Traveller was highly recomended by some fellow RPGers. I will look into these for sure.