DKIM & Emails - Google, PhpList & 123-reg

I have changed my DNS setup on my domains to have the registrar (123-reg) handle as much as possible, so server load can be reduced, however, I have now found out that they do not ‘manage’/accept DKIM.

Whilst I have several domains on the VPS, 2 are set up as follows:
1 - website on VPS
2 - email managed via google apps
3 - email newsletters via PHPlist on website

To try and increase the delivery rate of newsletters, I want to invoke DKIM on these 2 domains, but, as 123-reg does not allow this, and it is handling DNS, how can this be achieved? Or can it?

I have no issue using Bind on these 2 domains, but would want to revert to this as a last resort.

Thoughts and advice would be appreciated.