I'm a bit late in on this one and hopefully all is now well. I usually try to stick by a few tips I was given years ago!
- If you've got the facilities, yes, let them get to know each other over the fence for a week or two.
- Try to hack out together in the meantime - it's a natural herd activity

- When introducing them into the same field it's better if it can be neutral territory. And...
...make sure they're good and hungry when they first go out
