If DP's gone out of his way, or just made and handed me a cup of tea, then of course I say thanks.
If I'm cooking dinner, he asks what he can do, and I say can you bung on some chips, then if he reports back I'll probably just say "cool" - no need to thank, since that's just us working together to get tea done.
Can you just acknowledge that the task has been done rather than thank him, and therefore feel like he's done something that's really your responsibility as a favour?
Also, DP was given the choice of breakfast or bedtime when our second got old enough to go to bed on his own, and he picked bedtime - which is the easy one in this house - if he ever wanted a night off, just for laziness sake (ie. not if ill, or working late or similar), I only offered to swap a breakfast with him. I think it made him appreciate that the kids were his responsibility too a bit more (mind you, I'm still the one that got them in the bedtime routine that made bedtime the walk in a park it was, and he pretty much never read them a bedtime story, so it was still half-arsed on his part)