Some of the best memories I have from my childhood involve traditions that my family always did. Any time we all did stuff together (traveling, swimming, reading, playing, doing crafts, putting up holiday decorations, helping to cook) I always had a blast. Anything that includes your kids with the whole family is going to be a ton of fun for them. This list by Linz at Cuegly has 75 ideas for activities to do with your kids, many of which could become new traditions. Here are some that I used to do and always loved! :
Build blanket forts
Dinosaur Dig in the yard
Finger Painting
Make a book- then write in it!
Make hand shadows on the wall
Create your own silly holiday (like “donut day!”)
Go on nature walks