That's awesome. I have no experience with anything like that and have only had one chinchilla at any time but I've seen a lot of posts here on the board where people have had problems with pairing their pets together. If you try it the best I can recommend is to watch closely and have a way to stop them if they try to do anything crazy and certainly make it so you can disconnect the tunnel easily.
There actually are good advantages to keep them separate. The best one is that you can monitor the food and water intake of each one and watch for any kind of developing health issues as part of your daily routine. Of course the disadvantage is that it might be difficult to allow them to be together during playtimes.
I will warn you though that sexing young chinchillas is sometimes difficult and that sometimes unexpected breeding will occur when having a pair that turns out to be, well, a pair. And separating a breeding pair can be very difficult. I've seen that happen on this board lots of times. Make sure the person you get them from has good experience with that.