If your wife had sufficient PRSI contributions to qualify for JB, then she would be entitled to the personal rate - which is higher than the Qualified Adult rate. As she's been out of the workforce for some time, she may not qualify for JB though.
If your wife isn't entitled to JB then she may qualify for JA. It's means-tested and she will not receive any more than you would for her as a Qualified Adult. Depending on savings, etc, she may receive less than you would get for her on your claim.
(2008 rates for JA and JB - Personal Rate 198.80, Qualified Adult rate 131.30)
There would be additional payments for children (currently 24 per child per week) which would be divided between both claims.