Your mum probably knows it all already Liz but I am reading a book called Marshmallow Maths (recommended by the lovely Creations) and it has great ideas for what are the building blocks of mathematical understanding for toddlers and how to incorporate it all in daily life.
I have the Numberjacks book with me now and to give an example of the activities there is one where you have to draw a line from Numberjack 4 to things he might like from a group of pictures such as a dog with 4 legs, a square, a bunch of 4 balloons and other things without 4 associated with them (that presumably he wouldn't like). Then there are stickers you can add more things he might like to the group.
There are 5 almost identical pictures where you need to spot the odd one out.
There is a grid with most of Numberjack 3 drawn in and you have to draw the rest of the lines to complete the drawing.
There is a picture with questions below about how many numberjacks there are and who is in the lift, what colour tags are and whether there are more blue or yellow triangles.
There is a sticker activity where you have to sort things into groups such as things for feet (socks, shoes), flying things, musical instruments. Then it has a page for you to draw your own mixed up group of things.
There are many, many more. It is fun but definitely not all counting.