What you mean with grouping is actually called layouting in wpf. you pick a container which layouts your children.
Yes canvas is the most stupid container and so its the most lightest. grid has columns and rows which is very smart and stackpanel stacks its children depending on ortientation but canvas doesn't do anything except place uielements depending on x and y values.
Therefore I think canvas is pretty fine for your example since you want to have a bit of offset before you want to draw your figures.