I believe the iPad uses a version of Safari and pages generated by Second Site 3 should be fully compatible with it.
In terms of layout and/or Theme choices, here are a couple suggestions:
- Do not use a framed site. There's not enough width on mobile devices.
- Use one of the simpler Themes, one that doesn't include a lot of graphics. In particular, don't use graphic buttons, use the text and CSS buttons. They use minimal space.
You can make CSS changes to take advantage of the look of iPad (iPhone) applications, but you'll have to consult an iPad design site for that level of detail.