Tell him you've a TS fantasy and would he be okay cross-dressing for the evening? Stay indoors on a night when you know you'll be completely alone, talk to him about what you can agree he'll wear (stockings, thong, etc.) get him to have a shave and pamper him with some nice slutty make up for both of you. Get his phone out and take some photos for him on there of him going down on you and other things that would incriminate him more than you if they got out. Maybe even a video that you can watch back together. Tell him how good his stocking-clad legs felt against yours. See how he responds, he'll either be a tried it, thanks or talk about future plans - blonde wig, embrace your fantasy more, etc.