I don't see any problem there. Its true that we shouldn't gambling in front of children as it may effect them badly. But when its comes to mature people like you and your wife, there's nothing wrong until both of you guys can control yourselves, follow the discipline as well as able to manage economical status and become so responsible as gambler. Nobody need to quit, just mainly focus on primary income source and do gambling less or stay within limit. Don't spoil family moments , only gambling when get free time or children aren't around you.if you guys can't handle and worry about Ensure the healthy environment for children, then both can quit gambling together, otherwise there'll be a quarrel between you about this matter. So that is my suggestion
Even to say they can control their gambling habits but I don't think it was good to see both of them gambling. One of them must stop and I say that it was the wife. Besides, we are not talking about finances but we are talking about time spent with the family and bonding which is needed when you have a family or if you are building a family. Good relationships and communication between parents and kids are very important which they don't have to ignore for this will have negative results in the future. They should value their time with their kids as this will guide them on how to handle their family soon, or I'm worried they will get involved in gambling at a young age.