Holidays are for creating memories and its no wonder that some like to incorporate such memories in a grand gesture such as a proposal.
My thoughts on proposing during such an already high holiday is think of your girlfriend and if a public proposal is something she would want. Not everyone wants to be asked with family and friends around. If she is the type where this wouldn’t be an issue then I say proceed.
I would definitely make sure it’s a go with the host of Thanksgiving dinner. I’m sure they would love a heads up of the event as well. If you want it to be a full family affair, plan ahead of time. I mean you definitely want your girlfriend to know and see the attention to detail. Also be selective in who you tell in the family. Telling only key factors in your girlfriend’s family will keep the ones who will spill the beans at bay. Be clear on your intent to keep it a secret.
Another suggestion is you could ask her on Thanksgiving but ask her when the two of you have some private time. If you will be visiting family and friends then set aside a recap time of reflection. Thanksgiving can be fun but also time consuming too. My husband and I have always opened up a bottle of wine together and talk about what makes us grateful to have each other even when we were dating. It allowed us to have some holiday memories of our own. This could be the time you plan your proposal.
Most importantly keep in mind that she will think of this day over and over again so make it special. Let her know of how much she means and how grateful you are to have her in your life. Most importantly it’s the next step into your life journey together so enjoy the moment. This one question will change the course of your life as you very well know it. Good luck and hope all goes well.