I have been doing that for about 5 years now, and I have to say there are times my wife doesn't even realize that I am gambling. Not that I would ever hide from her but after certain amount of years being married, you do not just talk about every single expense, I didn't tell her that I bought a sandwich for lunch yesterday and that's about the same idea, it wouldn't be cared if I told her.
So just put in very small amounts, amounts that would not be even cared in family budget if you told your wife and then you will be fine, even if you lose it then you will be fine. I keep gambling with the same money over and over again without having any problems at all.
I know exactly what you mean, when you are gambling maybe 20-30 bucks a month, nobody even notices it because it is such a small amount, you do not even realize it is there until it is gone and then you keep going.
I do not gamble too much neither and nobody around me would even know that I gamble neither, I do not like to talk about it neither not because I am ashamed or something because I like it and I am proud whenever I win, it is just because the discussions and chats about them are usually very boring.
Gambling is something you do, not something you talk about or maybe it is just me, I am already chatting it with people around here, I do not want to do it with my friends. Hence, nobody would even know I gamble when I do not win big, I spend only small, and I do not talk about it. If you are in that situation, then you won't be in trouble, because you are not risking anything big in your life, not huge amounts, just enough to go unnoticed.