If your child is going to a friend's or relative's birthday party, ask them to guess how long it would take to get to that person's house by car, bus or train. Encourage them to round up to the nearest ten minutes e.g. Will it take 10, 20 or 30 minutes to get there? Afterwards, look at Google Maps or something similar to show them the exact time it's going to take.
If you're hosting a party or a family get together then get your child to help you plan how much food, juice or seats you'll need e.g. How many people are coming? How many sandwiches do you need to make? How many cups do you need for the children? Roughly what time shall we ask them to arrive?
Your child would love to bake a cake with you. Find an easy recipe (e.g. Victoria Sponge) online and go shopping together for the ingredients. Get them to help you find what to buy: 'How much flour do we need? Do we need a big or small bag of flour?' When you've finished baking, ask your child to show you how to cut it into halves, quarters, fifths or sixths.