I can fully empathise with your situation, my step-daughter moved in with us a few months ago and I have been in the same situation. TBH your options are limited and ultimately you will face situations which you would rather avoid.
Depending on the viewpoint of those affected you could sit down and discuss the issue head on - if they have any understanding of the trans or LGBT community this could be favourable to you. Often telling family and friends can be the most daunting prospect in your mind but in reality is no more a revelation than telling them that you enjoy going to the pub on a friday night and ordering cocktails instead of beer. Since your wife is aware and understands your needs, perhaps you could engineer a situation where you lose a "bet" with her and have to spend the evening dressed as a woman - your wife could then dress you and enlist your son's girlfriend to assist in transforming you. You could take this further by having your wife suggest that they utilise their skills to see how realistic they could make you appear.
Otherwise, it may be a case of taking opportunities as they arise or you could ensure that if they have a night out that they are absent longer - if they are going out, slip them a few quid to ensure that they are able to stay out longer.
With my step-daughter, my wife engineered the situation where she challenged me to wear a dress for the evening but allowed me to dictate what items were worn. A few days later we introduces the idea to our daughter that an "escape" of this sort would help alleviate the stress that I was under due to being my wife's main carer and having to deal with every aspect of day to day life. We are at the stage where I can dress if I wish but unless otherwise indicated will only do so when our daughter is either away or has retreated to her room in the evening. One unexpected benefit has been that as our daughter has studied beauty therapy she has given me a few makeovers when she has been confronted by my efforts to apply make-up and suggested a few alterations to which products I use.
My advice would be to assess the situation and mood, discuss the general subject in loose terms (plenty opportunities arise from news articles or even chance encounters with other cd's/trans people in day to day life). If the responses are favourable then you can progress towards the goal of compromise which allows you some time to indulge yourself. Remember that you have already faced the issue when telling your wife, so you have an ally who can help explain the needs of the situation - she could confirm that by dressing you are less irritable and more amenable to other suggestions.
"Denying who you really are, only leads to regrets later in life. Seize the moment because it will never come around again."
I have been reliably informed that I am a much bigger bitch when I am NOT Sara!!!!