The iPad 2 uses Apple's A5 processor which is based on the ARM Cortex-A9 CPU. ARM processors are 32-bit only CPUs, so all software that runs on these CPUs is, by definition, 32-bit. There's nothing to set.
If your daughter's homework requires a 32-bit version of the browser, then it's not the browser she's using. Web browsers themselves simply render HTML and interpret Javascript. In the browser, there's no sense of 32-bit or 64-bit; they'd be indistinguishible. The only time 32-bit versus 64-bit applies would be for a plug-in to the browser. Mobile browsers don't typically support plug-ins; Mobile Safari certainly doesn't.
Your daughter is not using the web-browser for her assignments, but rather another application that uses the browser to present it. In that case, you're going to need a desktop computer (or virtual machine) and operating system that meet that plug-in/application's requirements. Your iPad will not suffice.