You have to avoid intercourse for 6-8 weeks after vaginoplasty, so that may be a giveaway. And, aren't you hoping it will make a noticeable difference? That said, I have had patients whose spouses are not very observant and have not noticed after procedures that seem to have fairly obvious results to others.
Aside from if he notices, there are other things to consider. If you have a complication, not only might you not be able to hide it, but it will definitely make things more stressful for you and may even add significant costs. Even if you don't have a complication, he may figure it out anyway, and he might be more upset at being lied to than you doing the procedure.
Overall, my recommendation is to discuss your thoughts with your husband. Best wishes!