They are still very young to be 'learning 'concepts from worksheets especially if they are still hesitant about basic counting skills, many children take a while to be confident that 7 is always 7 for example. if your children need to recount small numbers of objects it means they haven't reached this yet. Try putting a few similar sized objects, say about 5 to start, (try toy cars or Lego bricks) , then ask the child to close their eyes, cover a few of the objects then ask how many have you covered, as they get more confident then increase the original number. Make sure they get the chance to be the one in charge of 'covering' while you guess.
Also try to encourage them to count on from a starting place that isn't 1, we've got eight Lego bricks , let's put some more out, 9,10,11,12, how many altogether.
Lots of other opportunities for number activities at home, especially as there are two of them! Sorting out socks into pairs then counting. lining up the family shoes in pairs, setting out cutlery/mats on the table.
Sweets like smarties are brilliant for number activities too , eg sort them into colours, which colour has the most, which the least, if I put the yellows and the Reds together how many smarties do I have altogether? How many more brown than red? What's the difference between the yellow and red? How many fewer blue than yellow? Five minutes then eat the smarties.