Not sure, never dealt with PB or savings bonds, but if you are interested in savings for them / kids accounts and all the tax issues etc. that go with it, I can recommend a great book.
"How to give your kids $1 Million each" (and it won't cost you a cent) by Ashley Ormond. Big blue cover
His other (red cover) book "$1 Million for life" is equally as good, it's more for "us adults". I have both books and I love his straight-forward talking style. It is NOT a 'get rich quick' book, but he does go into a lot of the tax issues and structures for kids savings etc.
Check it out at http://www.investing101.com.au
P.S. I know from Scott Pape's Barefoot Investor Blog at news.com.au that there is something called an 'education bond' (or something like that), but I'm not too crash hot on how they work. In any case, not holding an AFSL, I can only point you in the right direction - sorry !