Welcome back! Glad to see you're back into RC. For driveability, I would suggest against the Traxxas minis. Even I have a hard time controlling mine around corners as the laydown shocks are way too springy and make the vehicle high off the ground. I would highly suggest 1/10 scale for both of you, and both from the offerings of Traxxas. Here is what I would suggest...

Truck; http://www.horizonhobby.com/slash-2w...ody-tra58024t2

Batteries (this has 2, but you can only buy 1 if you want); http://www.atomikrc.com/collections/...-plug-x2-packs

Charger; http://www.atomikrc.com/collections/...attery-charger

For upgrades on the Slash, there are only a few I can actually suggest.

Rear hub carrier; http://www.atomikrc.com/collections/...-2wd-1-10-blue

Rear arms; https://www.amainhobbies.com/rpm-rea...FdgHgQodE1UFcg