This question is really all about personal prefference. I have both truggies and monster trucks and I love them all. But truggies will do just about anything and go just about anywhere a monster truck will and will handle better while doing it. I personally like my truggies better but that is just me. being in the situation you are I would get a truggy since you kids will have the MT. you will have access to both types. Of the brands you listed I preffer Losi over the rest but HPI is good as is Associated. I have never been impressed with Traxxas but that is all I will say about that.
My favorite MT has got to be the LST (or LST based models) They are so well built and handle very well. I have never broken anything on my LST besides the spur gear. I had a savage for a while and it was a good truck but I definently broke more parts with and it and it didn't drive as nice as the LST. I also have an Associated MGT 8.0 and that thing is just a beast. I have left it all stock because I have found it to be built like a tank! the only problem I have had with it so far has been that the grub screws tend to fall out but that is easily fixed with some locktite, and it is such a gas hog. but all the torque makes it worth it! I have had tmaxx's and revo's but I like to keep brand bashing to a minimun so I will just say I wasn't impressed with them and parts support was excellent!LOL!
As far as truggies go the only 2 I have had so far are the HPI Hellfire and the Ofna Jammin CRT X1. they are both nice but I love the X1. I spent quite a bit of time working on the Hellfire and I found the Diffs to be a weak spot for it. but it is laid out nicely and is easy to work on. I haven't had to replace anything on the X1 yet but it is easy to work on as well and is laid out well. there are alot of really nice truggies out there I would like to get my hands on but money is lacking
the losi 8ight has a good reputation as does the RC8T, MBX5T or 6T. The Thunder Tiger ST-1 is a little bit cheaper but I hear it is a very solid truck.
Sorry for writing a book but here is my 2 cents. Let us know what you get!!