They can't do the kinds of holidays they used to anymore because Chris can't be around people. It suits him to have them isolated in the van, they can move on frequently and now that they are vlogging behind no one can alert others at the same locations that they are there. He can't spend days playing around in the pool, he can't sit every day in a busy all inclusive restaurant. He's on edge enough when he sees anyone and anywhere that might be busy they go after dark and when everything is closed. With his hair/beanie combo, the amount of feral children and just the volume they all speak at, he also knows they could never blend in with all the other people around and even people that don't know anything about them recognise that these are people to avoid.
With all that they spend on the van as you say, it isn't about money so much as the need to keep moving/running away. That's why he can't stand being at home for long and will still go away even when the children are unwell. I think Sarah would be happier at home going shopping every day and mostly ignoring everyone except Mila and Jace, for all that she's living her best life travelling around she certainly seems miserable. She likes buying more useless things for the house, sofas, clothes that don't fit her children and eating, all of which are easier at home. Chris likes cheating on his wife and chatting up teens, both give a reason to run away and hide.
I’m probably just a heartless 
he is quite literally giving her this message choosing this song. The lyrics are as follows (baring in mind her so called step father picked this out of all the other songs he could have/should have chosen…)
who? Who in their right mind would take an inquisitive 3 year old near that edge and that ravine that was running towards the cliff edge 
