When you have an IR-1 in the process, but we decided to move to Europe is it then better to cancel that application or is it better to just let it go through the system and sort of cancel it at the point when we're invited for an interview?
Where are you in the process currently? Once the I-130 is approved my understanding is that you can delay at the NVC stage indefinitely. You just have to contact them at least once every 12 months, or log in every year to submit one or another document (basically they should see some activity on your case).