One of the activities I engaged my 2ndies in at the beginning of each school year was a game called Make 10. I made three sets of flashcards of the numerals 0-10.
To play, students started by sitting at their seats with heads down and eyes closed. I walked around the room placing a numeral card on each desk. All the leftover cards I displayed on the chalk rail. Then I said, "Make 10!"
Students would jump up and place their cards on their chests so that others could see it. Without talking they would quickly find their partner, whose number with their own equaled 10. When all the partners were matched up, children who hadn't found one yet could select the appropriate number card from the chalk rail. Then the partners would line up together. The ones who didn't have a partner would hold both number cards.
I would have the first pair come up and show their cards while standing by me. I said, "They say 2 + 8 = 10. Is that right?" The class would answer yes or no. If their cards didn't equal 10, I had the partners go sit down and figure out what their cards equaled. Then they could go to the numeral cards displayed on the chalk rail to choose correct matches and get back in line for a second try.
We tried to do all this as quickly as possible without talking, except for the yes/no. They had to compute the addends while walking around. They saw and heard the math facts. These actions helped their visual, auditory and motor memory to help cement the math facts to long-term memory. They enjoyed this fast-paced game and stayed focused. We usually played it two to three times, and each time they tried to do it more quickly.
I'm a firm believer in helping students reach automaticity in their basic math facts. They must master facts to this level in order to move on to higher level math skills. If I had a group whose skills were so weak they struggled with the sums to 10, I backed up to spend plenty of time on the sums to 5.
Try Make 10. Your young learners will love it, and you'll be moving them along toward automaticity. This was a good springboard to later in the 2nd grade year when we played Make 100.