It depends on what you do but I think it is harder when children are older.
My son is only 5 and so far we haven't really spent much this week. He has done a 5 day intensive swim course (so a 30 min lesson each day) - he absolutely loves swimming and he has really progressed this week so it was £25 well spent. It also meant that with getting there, getting changed and lesson it took up most of the afternoon!
Monday we saw my mum in the morning and she came to watch swimming so no extra cost.
Tue we had an appointment in the morning and then played outside at home before swimming so no cost.
I had to pop into town on Wed morning so we did that and DS had a couple of turns on rides so a couple of quid there. Plus, I took him for lunch before swimming.
Thur/Fri we played at home and DS 'helped' me tidy and we went to swimming in the afternoon.
I am lucky that his usual weekend activities of drama and swimming still run in the hols and we see my Nan and Aunt on Saturdays which he loves.
Not sure next week - will go to the library/park/go swimming ourselves for fun /planning a day trip with DH/baking at home.
So a mixture of things that cost and free things. As I say though, older kids are harder to entertain imo.