We used to get a summer au pair to cover the long summer holidays, then the other weeks were shared between me & DH. I was able to buy extra holiday at work. I usually arranged for DC to go a friend's on inset days.
DH and I take 2 weeks AL each, one of those weeks we take together, so we cover 3 weeks in total.
Use play schemes for 2-3 weeks. My parents live nearby but are not well enough to have dcs for more than a day or two here and there, so they cover any half weeks iyswim - so the first few days of hold, and then the last few (inset) days.