Tin Can Alley
Collect cans in advance of your fair and make sure they have no sharp edges. Pile the cans in pyramids of three, six, etc. and give players beanbags, balls or even a nerf gun to try to knock them off. The more cans knocked down, the higher the score. Paint the cans to fit your theme.
Set up three plastic buckets of different sizes in a firing line, with the largest nearest to the player and the smallest furthest away. Give each contestant three shots at throwing a ball so it lands (and stays) in a bucket. Can give a number of points for each bucket and a bonus if they get all three in a bucket, or if they get one in the smallest bucket.
Egg and spoon
Dressing up race...
Float some toys/plastic items (doesn't have to be ducks) in some water (paddling pool, bath, washing up bowl...) and scoop them out. You can use a net to scoop if you have one or even a bucket taped to a stick. Especially good for little ones.
Fiendishly hard, you could actually do this with pocket money or leave it on the counter all week and give the collected coins to charity. Float a lemon in a bowl of water and challenge players to balance a coin on the fruit. If the coin balances, they win, but if it falls off they lose their money. .
Challenge players to use a spoon to get as many marbles as they can into the hole on an upturned ceramic plant pot in one minute. Keep a leader board and see who's on top at the end of the day. You could even paint the pot to jazz it up!
Pin the Tail on the Donkey
...or pin whatever you like on whatever seems appropriate! Draw or print out a tail-less donkey. Create a tail with a sticky end - blu tack works well, or you can make a tail per player and have them tape them on. Blindfold players and invite them to pin the tail on the right place.
A messy sensory one! Put jelly in big bowls and fill it with little plastic toys or fairly solid sweet treats. Children dive in and dig out the prizes - yuck!
Use what you've got to make this work - nerf guns, water pistols, catapults. Balance ping pong balls on the tops of plastic bottles filled with water to weight them down and try to shoot them off. See who can knock the most down given a certain number of shots or amount of time.
Gather some hats, glasses, fake moustaches or other wearable items, make a cardboard frame and take some silly pics of yourselves. Then put them in your lockdown scrapbook!