sometimes betas think the gouramis are other betas because of their shape and size. So just keep an eye on them and have a backup plan if they start fighting. otherwise I like where your tank is going. Another caution is having 3 gouramis in there could turn bad if two of them decide to spawn as the parents will get very territorial. so I guess I would suggest either going with the beta or 2 gouramis. Three would be fine if your sure you can get all the same sex.
Just some suggestions. Happy Growing!