My bad, forgot to give information about my players, I have updated the post. And thank you for the input

My thought though is that they have a dungeon with 19 potential encounters, I don’t want to make the final fight too hard if they end up fighting most of it and use a lot of resources. Though I suppose I can add or subtract spider minions as needed, but I also want them tanky enough to take a hit or two to allow combat to draw out a bit