Childcare for a 4/5 year old for a week in May?

I am reaching out to our wonderful community to seek assistance with a childcare challenge my family is facing.

My son attends Growing Light preschool in Oakland, which will be closed from May 14th to May 22nd due to the Greek Festival. During this period, I will need care for my 4-year-old son while I am at work. However, our home hosts his two-year-old sister and her nanny share friend, along with the nanny herself.  Unfortunately, the limited space and demands of caring for two active toddlers make it impractical to add another child to the mix, even if we were to hire another caregiver just for the 4-year-old. Asking our nanny to manage an additional child would be unfair and overwhelming.

With traditional camps unavailable in May, I am seeking suggestions or resources from the community to help tackle this childcare conundrum.  Any advice or recommendations would be immensely appreciated.