How can I prevent sudden increases in shower water temperature
Adjusting the whole-house water pressure is unlikely to solve this problem, simply because you set your shower temperature based on some initial balance of hot and cold. When other people draw cold water only, the pressure difference will still have the potential to affect your shower temperature.

Instead, you should get a pressure balanced valve or shower fixture. These fixtures automatically reduce hot water pressure when cold pressure falls, so instead of a temperature spike you simply get a momentary decrease in output pressure. You can find pressure-balanced fixtures (which would replace your existing shower fixtures) or an independent pressure balancing valve (which you'd want to install near the shower but would allow you to keep your existing fixture).