Different destination URLs for Search Network & Display Network

[Grant]

My API app currently only utilizes the Search Network.  I'd like to add support for the Display Network, but I'm not sure which method I should use to generate different destination URLs for the search network and the display network so I can track their conversions separately and set bids appropriately.  I've come up with three ideas:

1. I could generate a duplicate set of campaigns and ad groups for the display network and set different ad destination URLs.

2. I could set individual destination URLs for each keyword in each ad group and use the ad destination URL as the display network URL.  Would that work?  The idea is that the search network would use the keyword destination URLs and the display network would use the ad destination URL.

3. Is there a way to associate certain ads in an ad group with the search network and certain ads with the display network?  Then I could have different ad destination URLs for each network.

Which of these methods would you choose?  Are there any other possibilities?

[AdWords API Advisor]

Hi Grant,

I think the option that is the simplest to use is the {network}
ValueTrack parameter:

http://adwords.google.com/support/aw/bin/answer.py?hl=en&answer=178489

You can use this parameter in your ad URLs and the value will be
either 'g' for Google Search, 's' for Search partners, or 'd' for the
Display network.

Best,
- Eric Koleda, AdWords API Team