My Reception DS needs help with numbers

You & your kids: 

My DS (4 and a half)  started Reception in Sept, has made lots of friends and seems to be very happy.  His TA came to find me the other day to tell me that he's struggling to recognise numbers and that it would be good if I did some more work with him on this at home.   I'm really glad that she told me, as whilst I've been enthusiastically reading with him since he was tiny, I now realise that I've hardly done anything with him involving numbers, apart from the odd rendition of '12345, Once I caught a fish alive'!  
  We haven't been given any 'homework' as such, so I'm looking for some ideas for games or activities I can do with him.  I've downloaded the lovely resources on this site (thank you School Run!) but would welcome any other suggestions.  Many thanks.