a natural cook, and I find it really challenging to get any cooking done now that I have a baby. So don't beat yourself up!
How I come up with "what to cook" when I'm not inspired to cook anything in particular is to think of it as a kind of column system:
1 cooked vegetable
1 raw vegetable
Then I just fill in the blanks based on what's in the fridge/freezer/pantry. We eat meat, so that might look like:
chicken breasts in honey-mustard sauce
Or I can combine columns or leave them out, if I'm desperate. Like:
grilled cheese sandwiches (starch+some protein)
tomato soup (this totally counts as a cooked vegetable, haha)
carrot and celery salad
When I'm doing more one-pot/casserole/crockpot meals (which I love for the time savings, but I have to plan them in advance, I can't just start cooking 40 minutes before we want to eat), I think of it more like:
something with vegetables
So that might look like
black bean soup
I agree with the PP that it's a great idea to make a list of everything you know how to cook, and just stick it on the fridge. You might even sort it into literal columns, and put how long it takes to cook behind each item. Then when it's time to cook dinner, if you haven't preplanned anything, you just grab one from each column:
You mentioned that you like sweet potatoes (so do I!) - they are such a great dinner item. You might serve them with a protein and a veggie, and a really quick version could be:
sweet potato with sour cream (10 minutes in the microwave)
salad (tear open bagged salad, toss with vinaigrette)
For something like this, all you'd have to do would be the potatoes, either in the microwave (wrap them in foil afterward, they'll stay warm for a while) or toss them in the oven in advance. When your husband gets home, you hand him the baby and steam the broccoli, toss the salad, and cook the omelet. Under 10 minutes from when he walks in the door to sitting down to dinner.
Do you wear your son? Mine sounds like yours: he wakes up a lot if I leave while he's napping, but if I just put him in a carrier and do prep, he'll often either tolerate it or fall asleep.
And, about sitting down to dinner: it's important to us that we sit down to eat whenever we can, but our little guy often declines to be put down. So, um, he's had some food dropped on his head. Them's the breaks.