You're using the default padding, which aligns variables on a boundary.
A char is defined to be 1 byte. But althought a bool represents 1 bit, it isn't necessarily represented as 1 byte, it can be represented by an int. It wasn't introduced to save space, it as introduced to allow overloading on a logical value, rather than a numeric value.
The private-member children shows as 16 bytes which got me curious.
I understand there could be padding but could anyone provide a breakdown as to how 16 bytes come about?
It is implementation-defined.
Depending on the compiler/platform I just tried, I saw sizes of 12, 16, 24, 32 bytes for the children (with the size of Node, respectively, 16, 20, 32, 40 bytes)
To learn about the details of what's stored in the object representation of the vector you're using, you'd have to examine your library code or load the program in the debugger. Typically, there are three pointers (start, size, and capacity) and the allocator (at least as of c++11).