I was a single parent of 3.
Timetable for holidays was great. Look out for free activities - sports in the park, library events, we did the reading challenge every year at the library, try Groupon see if they have any cheap days out (eg laser quest is usually £5 for 2 games at ours) as a special treat, cheap cinema mornings, free museums, picnics, baking, making pizzas, older ones could be given £5 and need to cook a 2 course meal for all of you. Meet up with friends, cheap swimming, we have a council run country park near us charge £2 for mountain bike hire.
Re house our rule is every morning get washed dressed tidy room, make bed have breakfast then one chore each before any electrical. Also are they old enough for washing pots etc we have rotas for that.
Swimming, outdoor paddling pools, or we just go down to a stream with picnic, towel and change of clothes, give them a task to make a video about something make it a competition and do a screening, make a den in garden, have a movie afternoon with popcorn, bake off.
Routine is my top tip - everyday wake up time and bed time same, one planned activity per day, read, hour on PS, chore, older one may have homework/ revision, eldest does volunteering once a week and has a little job one day a week.
And lastly it doesn't matter if house is a mess during day get the kids to help tidy it at end of each day it'll take less time and mean they'll think about mess they make in mean time!