No, it will only end in tears. No good can come from pursuing this obsession.
It is easy to see why this kind of thing happens. Your mother-in-law is an older version of your wife, and with her being widowed, it is inevitable that your feelings for your mother-in-law have grown, partly out of a desire to comfort and protect her.
You must resist temptation and avoid putting yourself into situations where your curiosity might get the better of you. These feelings have more to do with male fantasy than real emotions, so leave it at that; no man should get between a mother and daughter; it's a complex enough relationship at the best of times.
It's unlikely that your attraction is mutual, in any case. Even if your mother-in-law is now in the market for a relationship, it's far more credible that it will be with someone of her own age group. Possibly someone she has known for a long time as a friend.
How about DANG NO! Like N O !!! Would you stand up on your chair and strip naked at a family Thanksgiving? Most things that you THINK will stay secret do NOT stay secret. The weirdness of these relationships being strained in that way will make it very hard to keep everything else normal. Even if you are correct in thinking she is attracted to you, she may be able to feel that way while it DOES NOT seem likely that anything will happen. If you try to make a move, even if you were right initially, she may be suddenly horriifed at what it would mean IN REALITY, and may then blame you (even though that is unfair, even if she was in fact entertaining the thought). She may have a very hard time keeping this to herself. And women always "mis-remember" things to suit their emotional reaction, so she will make it sound far worse than it really was. It could end up destroying your entire family. If you are insistent upon committing adultery against your wife, perhaps you could try someone a little less risky.... Like your boss' wife.... A CIA assassin's girlfriend... A judge's daughter... Someone "safe" like that.
I don't think this is a good idea at all. You would only hurt the whole family and it would be the end of your marriage and relationship with your mother-in-law. Your mother-in-law would probably be horrified if she knew what you were thinking. I don't know why you think she might be interested in you. Most mothers-in-law show affection as a motherly thing to do and you are thinking of betraying that trust. Your wife would never forgive you and you risk unfairly implicating your mother-in-law if your wife guesses that you have ideas about her mother. Mothers are very protective of their children and few mothers would ever betray their daughters in this way. Perhaps your marriage is over for you, it might be a good idea to keep away from your mother-in-law while you sort yourself out. Don't do it.
That's not exactly a good idea. If you have these kinda feelings for her then you need to try to put an end to it. Try not to think of her in that way. After all, she is your mother-in-law....If you go on with your feelings then it might end in pain and turmoil. I know you don't want that kinda friction between you and her. So try to block those kinda feelings out your mind.
I don't think you should try to find out if she's sexually attracted to you for a very simple reason, YOU'RE MARRIED. Even if she would be, think about YOUR WIFE, how you would hurt her, don't be so selfish, think about others around you and as you said it's just a sexual atraction. Are you ready to trade love for sexual atraction, for me it would mean that you don't love you wife that much, otherwise you wouldn't think like that.
Think really hard before you do something you'll probably regret later.
Have you considered how this would devastate your wife? This is a moment of lust that is embedded in your mind that you need to overcome. You should have never allowed your thoughts to stray in such a direction. If it was me and I found out I would be so hurt and heartbroken at the idea that you would even want to pursue this fantasy with my mother. That is not fair and marriage is suppose to be sacred between a man and his wife. I am not judging you but you need to consider the long-term affects of a short-term act of lust and possible humiliation. If the mother in law has flirted also that would be wrong. If she has not flirted, which she probably has not, then you need to focus on your wife and family and ask for forgiveness. Do what is right.