Sorry you are feeling so overwhelmed. I would feel the same if I didn’t have any time by myself for six weeks. And I understand that your older dc being here means the younger dc wiii be downstairs with them and it will be busier as a result.
I think you have to manage somehow today op and if it’s really too much, go upstairs to bed after lunch once everyone is settled claiming exhaustion or a headache. 💐
But for the future, I think it is really important to use this situation as a catalyst to do holidays differently from now - you are allowed a break too - and during ordinary “term time” build in time for yourself a couple of times a week that is just for you.
I made the same mistake when raising dc and and kept thinking a less busy period would arrive by itself but it didn’t and I came to realise that no one else was going to say “take time for yourself” you have to build it in to your weekly diary and make it happen and protect it ruthlessly. You don’t need any one else’s permission to do this. Your teens will be happier if you are happier. And they watch how we balance our life between work and pleasure.
I thought that your dc would be younger when you first posted. I get that four dc is a lot! Exhausting in fact. If they are teens though they don’t need you to be there physically as much. But I very much understand the emotional toll raising teens takes.
Can I ask is this just a holiday situation? Or do you need to adapt the way you parent to being a bit more hands off now they are older? Stepping back a bit? Letting them sort their own problems out more? Parenting alongside them rather than top down?
Is your dh stepping up enough? Are you getting enough support with housework and driving the teens around?
Can you re-think next year’s holidays? Can you take a week somewhere by yourself or with your husband in the middle of the holidays while your teens fend for themselves or go off to camps somewhere? It depends I guess on how old they are.
Take care op, I hope you feel less exhausted soon. Please try and protect well-being as parenting teens is a marathon ands it’s a surprisingly demanding period of life. 💐