Thanks for the responses so far!
I agree with AiRgeek for continuing to code with the resources I have. The current setup will work, I'm looking for future expand-ability as well.
Regarding the motors, I'm looking at high torque with a relatively low speed (3-5 MPH max), able to propel 30-40 lbs (25 lbs for the "vehicle", maybe a little more with the battery), hopefully a 4 hour battery life (there will be a lot of start and stop, primary function is entertainment), and both forward and reverse capability.
Ideally, I would like to start with slow acceleration because the environment may have multiple people in the area and would avoid "high speed" collisions (especially at initial movement). I haven't worked with motors at all yet, but have some ideas. I would think that the microcontroller would help with acceleration if it's programmed correctly.
Cr0sh makes a good point on the vehicle. I think building the unit would be the best option. I'm basing the project off a previous version, so I have some ideas on how the tricycle option will work. And you're right, mounting the motors will be a challenge.
I am interested in the local internet option though so I can see if it's a good option. If anyone has any resources on this, I'd be quite interested.
I'm not totally opposed to "throwing money at it", within reason. The project alone has so many interesting pieces from electronics, sewing, fabrication, and probably a few more I haven't thought of yet! I consider it a challenge to my hobby.