Yes, you can scale this up for 25 people, and since you’re serving a crowd, having extra baked beans isn’t a bad thing. The biggest issue you’ll run into with a larger batch is getting the sauce to reduce properly. I would not put a 4x batch into one deep baking dish because the greater depth will slow down evaporation and you could end up with very runny beans. I’d divide the finished mixture between multiple 9 x 13-inch baking dishes, keeping the depth fairly similar to what you see in my 12-inch skillet. Bake them uncovered at 350°F and start checking around the normal 45 to 55 minute mark. If the sauce still looks very loose, give them more time, checking every 10 minutes. Remember that you want to take them out while the sauce is still a little looser than you ultimately want because it will continue to thicken during the 10-minute rest. And don’t forget to divide that final addition of cider vinegar between the pans after they come out of the oven. For a buffet of 25, I’d probably make 3x, but 4x is completely reasonable if you want to make sure there’s more than enough.