What are some ways to help keep my body tempurature and feet warm when attending lengthly cold events?

Bundle Up. Wearing warm clothing is the number one answer. Second - try drinking warm beverages to heat up the inside of your body. Lastly - there are warm "packs" that you can get to safely keep feet and hands warm - check out your local "outdoors" store.
Good Socks... Thorlo socks are made for a great variety of athletic uses and specifically for some cold weather applications. Check out their web site and search "cold weather." (https://www.Thorlo.Com/).
Warm. As stated , warm drinks help and warm packs for your boots or shoes and bundle up means dress appropriately .