I have 2 DCs, aged 3 and 4. They are funny, fabulous, smart little people, and I really do love spending time with them. BUT. Right now I am finding them fecking exhausting, and we're only 2 weeks in to the summer holidays.
They're generally pretty well behaved apart from having the odd moment, and whilst they do fight, I don't think it's more than the average sibling relationship.
What I do find draining is the CONSTANT demands for me to do things, and also the incessant talking. They were both very early talkers, and DH and I are chatty people, but they are relentless! DS will constantly ask me questions I just can't always answer (normal, I know), or waffle on about his particular interest for the best part of the day. DD will narrate everything going on and the stream of consciousness going through her head NON STOP, and if I don't appear to be paying attention, will now say to me "Mummy, look at me, look at me please" until I totally stop everything. Which is fine sometimes, but I can't do that 24/7!
I work for myself, and in the holidays I have to do it in the evenings (freelance here), but by the time that comes, I just feel so drained. I know I should be grateful that they want to engage with me, and I love them to bits, but I've been getting a bit snappy with them as I can't/simply don't want to DO STUFF or be 'on' all the time. They have plenty of time with me, and I always make sure we do several things together throughout the day and have quality time eg. reading, a game, just talking to them about what they're doing, so they're not deprived of attention. We also get out and about loads, but again, we can't do that every day (and I want a rest!).
The other day I shouted at them when DS tipped me over the edge asking me to get yet another activity out for them, 10 minutes after I'd set up a previously requested activity, because I just felt suffocated at the demands. I took myself off upstairs to have a little weep! 
They are very early risers whatever time they go to sleep (5-6am), and they have some stamina, keeping on with this right up until bedtime. DD also still doesn't always sleep through the night, so I think DH and I are quite tired from this too. I just can't keep up!
Is this normal? Does anyone have any advice as to how to deal with 'high needs' children? Or just please tell me I'm not the only one?! The only time they are quiet is when the telly is on, but I don't want them watching it all the time (I tend so save it for some down-time late afternoon when they need a rest and I need to cooke dinner).
They are awesome but very full-on!