There's sooo much good stuff for the little ones on the iPad that's really educational. Android is simply lacking in that respect (for now).
Case in point, I downloaded some apps, and without any intervention on my part she taught herself how to write letters (little skywriter), do simple math (monkey school math), work with sets (firstapp.com peeps), draw lovely artwork with commentary (doodlecast), learn about physics (amazing alex) etc etc.
Nothing better than having her come over to me and "explain" how things work.
If you think an iPad is going overboard in terms of expenses, a lot of this stuff works on the iTouch as well.
And this looks promising too (more like Cargo Bot) http://sourceforge.net/projects/andmaz/