
As bevb said, let them meet on neutral territory. Ideally, it should be off leash, which from the sounds of it shouldn't be a problem - this will allow both boys to communicate properly with each other without a leash restricting them in any way.
A word of caution: whilst I'm sure you'll be fine, male dobes are notorious for not getting on with other male dobes, especially in the house - at 9 months I wouldn't think there'd be any problems, but I just thought it was worth mentioning.
Have fun, I expect your house will be a whirlwind of trouble for a week!!