If the OPs kids are too young for a 12A film they are pretty easily entertained with what is currently open. It is teenagers that I would be more concerned about.
Years ago parents didn't take kids to venues that cost money all the time. There would have been a few treats but lots of days of entertaining yourself.
There is plenty for kids to do with what is open now, and a bit of boredom is good for them.
The weather is glorious why would you want to be stuck in a cinema? Get outdoors, have a water fight or chase them with the hosepipe, wash the car, do some gardening. Make a picnic and take it to the park. Camp out in the garden. Play football/rounders/cricket, or something like tag or grandmothers footsteps. Go for a bike ride or a walk in the country, go to the beach. Read a book together (the libraries might be closed but they have e-book services). Play a board game, or a card game. Make a scrapbook or time capsule.
Arrange to meet another family outdoors for a picnic and games.
Have a BBQ and get the kids making things - not just the food you can really stretch this over a few days if you want with meal planning, shopping, writing menus for the restaurant, making a table centre and place mats, wrapping the cultery in paper napkins, planning and making a non-alcoholic cocktail and decorating the glasses, making ice-lollies for pudding, being a waiter etc. You can theme this too and incorporate some educational elements, so a bbq one week, next week an italian theme, then french, mexican etc and learn a bit about the country and some words of the language.
Put on a play, concert, poetry recital or puppet show for the adults.
Learn some new skills, a few cheap ideas depending upon ages would be:
Making a simple cold meal
Making a hot drink safely
Cooking a simple meal
Baking a cake or biscuits
Baking bread without a bread maker
Sewing a button on
Embroider a basic sampler
A simple hand sewing project like a face mask, hair scrunchies, bunting etc.
Knitting/crochet/macrame
Make your own play dough and make something with it
Read a map and do a simple orienteering task.
Use a compass with a map
Identify birds/butterflies/plants
There is so much you can do that is much more enriching and memorable than a cinema trip.