Ok this is what I think.

That first link you just posted of the Teamlosi xxx-t RTR Is I think idea for them.Its a VERY strong truck that comes with th best Speed Contol of any RTR (DOnt have to upgrade)I Race competivly and I still sue mine.The Losi also come swith a digital raio.Not to mention its top of the line.The thing I like aobut the losi it is.You said you wanted them to race too.Well with this truck they can tear the heck out of it learning....Then when they break parts (They will I promise) you can replace it with graphite.Also the motor it comes with is very raceable, and when it coms tiem to race all you have to do is get new tires/motor/and a little shock work and you have somehting that Way more compestiive then any of the evaders.

Now Since it comes in two colors...Make sure to get them 1 of each.The channel of the car goes by the body color.That way they can drive at the same time.

Now that You got that out of the way you need to look at the second most important thing in racing.Your bateries.The GP3300 batteries listed abouve are great to start out with.Make sure to get atlest 2 of them each.You can run those packs any more the 3 times a day or they will go bad.

Now to keep you batts up you need a nice charger.Again the Piranna listed above for 50$ is a exelent choice.Make sure you get two bwcuase when racing you dont have much more time then it takes to charge one battery between heats.

Now that you have all that your ALLLL set.CHarge those packs up and let me rip on those guys.Now remember!!!YOU ARE THEY PIT MAN.So when they break somehting you say "its fine son go play and ill get it fixed"If you expect them to work on them their going to lose intrest.Plus you want them to concentrate on driving it and not working on it.

I know alot of guys at my Local track that dont race.Just their kid(s).There very good and around the same age as your boys.It will take time but they will get it so work with them.

Another thing...prepared to spend lots...lots....and lots of money.....

Have a good time
Skyler

PS take the advice I just gave you and you WILL be happy.I promise.Also I can give you a number to where you can get the trucks for 229.99 a pice PM me.