Subitizing = immediately knowing how many items lie within the visual scene. I thought I'd include the definition since I just learned this word last year after teaching K for 8 years! My kiddos love working together to sort these cards out - so I thought yours might to. There are 6 sets of cards: numerals, number words, tally marks, quantities, ten frames, and addition problems. Granted, that makes this activity not 100% subitizing, but it builds number sense nonetheless. Included is a photo of how I use the subitizing cards.
I simply draw out a sorting table on a big piece of paper. I laminate it and then stick little pieces of Velcro on it and the back of the cards. The Christmas cards included in this pack go up to 12. I use this as a math workshop with 5-6 students working together, but you may have some other great ideas in mind. Enjoy!