R2D2 Project - Am I buying the right battery?

Going to start a project to mod the Hasbro Interactive R2D2 to be controlled either with an Arduino or a Raspberry Pi. The toy currently uses four "AA" batteries for the logic board and four "D" cell batteries to drive the motors. I want to replace that with a single LiPo battery.

I'm new to powering projects with batteries, but I have been doing a lot of reading. Here is what I was planning on buying:

LiPo 7.4v 5500mAh with PCB protection circuit:

Switching BEC, configured with either 5v or 6v with a regulator:

Universal charger:

The toy itself:

Does this seem like what I'd need? Is it underkill, overkill, or am I missing something? Any help would be greatly appreciated. Thanks!

It looks a nice matching set to me.

I would prefer a single cell LiPo battery. If two cells in series are used, one cell could get charged more than the other, or one could get damaged.
This is almost never a problem, but I just happen to like using just one cell.

The charger looks a little weak. 500ma max and it doesn't appear to have any cell balancing features; just a straight 500ma charge?

This charger requires an external AC adapter (wall wart) but generally a much better charger.

Chagrin is right.
You could use the battery packs used for RC.
With cell balancing it is no problem to have a few cells in series.
With a higher current to charge the cells, cell balancing is required.