if your Mac and iPad are on the same WiFi network, the bookmarks and settings for Safari that you make on your Mac should reflect or carry over to your iPad.
Nope. He needs to turn on bookmark syncing on both devices for that to happen, it doesn't "just happen" by dint of being on the same Wi-Fi network.
Make sure that Google is the search engine of choice on your Mac.
I think we are getting a little confused here.
The OP, as I read it, wants to make his *default homepage* the Google start page. This has nothing to do with the "set default search engine" preference one would see on desktop Safari, that pertains to the search bar not the default homepage.
(aside to point out that by default, the URL bar in iOS Safari *is* a Google search bar, so there's really no need to set Google.com as your homepage, but if you still want to ...)
To set the default SEARCH ENGINE for Safari in iOS, go to Settings->Safari->Search Engine. To the best of my knowledge (apart from a "cheat," hang on for that), you can't set a "home page" in iOS Safari -- it always returns to the last page you visited, so you can make it your "home page" by making google.com the last page you visit before closing Safari.
*the "cheat" I mentioned is that you can set any website as a program icon by itself by visiting the page, tapping the "share" button and choosing save to home screen. This creates an icon on your device that you press INSTEAD of the Safari app icon -- it opens Safari and takes you to the desired page, like a "home page" would.