ok as you said an 8 year old I'd strike the LX2 off the list as I said earlier as that thing would clear most driveways in like 2-3 seconds(unless you own a mansion with one of those quarter mile long driveways)
Seriously 1/8th scale RC's are mostly stupid fast(think 40 MPH), and can really hurt someone.
If you want something slower, and don't mind building you could look at the Tamiya DF-02. They range in price from $130-$170ish for kits (the $170 one has a better ESC included in the box) it needs around $30 in parts aditional, and a battery, and charger. Also one slight modification should be done right out of the box as it increases durability like 10 fold, and fixes its prime weakness. Own 2 of them, and got my nephew one a few years back. All in all total cost would be $240ish-300 to get all the gear to run em (including battery)
HPI Wheely King 4 WD Monster Truck that likes to uhh pop wheelies
Waterproof, comes RTR with controller, and battery (although the battery and charger are pretty crappy like in almost all RTR's). Think stock it goes like 12-15 MPH, but due to its large tires it can drive on a lot of surfaces. Will say it does like to tip if you turn at high speeds, but as its a solid axle Monster Truck so that is expected. Own one of these also. they are durable as long as they are not pushed to the limits (I mean we had one member here that made his go like 45 MPH, had it jump his moms Van, and complained it broke lol) Would recommend getting a better battery, and charger which will be like $70
The Vaterra's I mentioned earlier too I'd keep in as they are pretty tough, and IMO as much as I hate to admit it are a WAY better deal then the DF-02(also the DF-02 is the 1/10th scale buggy I compared it to).
http://www3.towerhobbies.com/cgi-bin...&I=LXBWEP&P=ML SCX10 let my nephew drive one, and he had a blast as it looks like a real truck, and due to the design can drive over quite a few obstacles. Also only goes like 10MPH will need a battery, and charger though so that like before is like $70 more on the total
But it also has a ton of accessories to modify it with like currently I'm trying to get a working snow plow for mine if the place would ever get them in stock (it costs like $100, and coulda really used it today with the snow we got...)
As far as Gas I'm guessing you mean nitro (as even the cheapest gas RC's are absurdly expensive), and honestly as much as I like them in cases with children I wouldn't recommend them. one of the reasons is the engines get over 240 degrees, and its VERY easy to get a bad burn specially when tuning the RC. Which brings me to the next part tuning its not for everyone now if you like fiddling with the RC, and don't mind spending a few minutes getting it to run properly then nitro might be fine. Other things with nitro if you don't have a hobby shop nearby (as nitro shipping prices are insane), and don't mind spending $45-50 a gallon (that was last time I bought one 2-3 years ago) then yes Nitro is fine.