The latest news as of 23rd March is that schools will be able to provide meals/vouchers:
https://www.gov.uk/government/news/plans-set-out-to-support-pupils-eligible-for-free-school-meals

In many schools, free school meals will still be available, but this will not include the universal free school meals given out up to Y2. So those with children this age or below will need to check if they are eligible on their local council website.

Your kids’ school might well be aware of this challenge, so start by asking a friendly teacher there. (Some schools are trying to keep meals available even if they’re shut.) If not, hopefully they can point you towards somewhere that is supporting parents’ in your position. If money is so tight, you’re going to need to be as resourceful and creative as you can be.

Do a search online for ‘cheap meals for kids’, there will be recipes and videos with ideas and suggestions. Ask around to see how other parents are coping – maybe you could team up to share batch meals between you. There will be family support available at community centres and at the local council and if you’re renting from the council or a housing association, society or charity, they might well have help available.

You don’t need to start foraging or poaching but you may need to start asking for help. It’s worth doing a search on Facebook for local support that is springing up – type your town or village into the search bar. Look through the other food related questions here too, to see if they inspire you with some ideas.

Schools will be able to provide meals/vouchers:
https://www.gov.uk/government/news/plans-set-out-to-support-pupils-eligible-for-free-school-meals