I’ve got a “late 2008” MacBook Pro that connects to sites ok in Firefox. That seems to be the browser that does the best at long-term support for old Macs.
Both those machines will run the latest Ubuntu just fine, and the latest Chrome (or Firefox) on it.
Just copy the LiveCD image onto a USB stick, insert, boot holding down the Option key, and you can try it without actually installing it (i.e. leaving your MacOS untouched).
