Use of cookies in fixed-layout EPUBs

I am creating a fixed-layout picture ebook in EPUB2 format to be published on the iBookstore.

In order to start some CSS3 animations at the same time on both pages of a page spread, I'd like to use a mechanism to synchronize the start time for the animations. This is because I noted that, in the iBook reader running on my iPad2, the left and right pages of a spread get loaded at different times and usually the right page is loaded approximately 1s later than the left page, though the delay is extremely variable.

I am thinking about using some javascript to set a cookie in order to check whether both pages in a spread are loaded and consequently start the animations. This is based on the assumption that both pages of a spread use a webview built upon the same common Safari rendering engine which uses a single set of cookies.

My questions are:

1. Is it allowed to use cookies in an EPUB to be published on the Apple iBookstore? On page 29 of the iBookstore Asset Guide 5.0 it is specified that "Books must not rely on external resources", but are cookies to be considered "external resources"?
2. If cookies are not allowed, is there any other way to synchronize the two pages of a page spread on the iBook reader?