I'm glad your surgery went well, I wish you the speediest of recoveries.
I reckon your best bet is going to be making and baking. Hobbycraft is a great place to start for both.
Making
Piggy banks (balloon, papier mache, paint)
Costumes
Pillow fort for a movie night (we used to toast marshmallows over candles - you'll ideally need an unscented, undyed, beeswax or soy candle)
Anything with glitter and stickers (sorry)
Baking
Marshmallow cakes (melted chocolate, marshmallow, smarties)
Cereal cakes (cereal, syrup, melted chocolate)
Shaped cookies (can get really interesting shapes in Hobbycraft, and if you're not up to actually making cookie dough you can buy that in any big supermarket - decorating them is the best bit anyway)
If your DCs are naturally competitive then coming up with competitions for the two of them could be fun - who can make the best boat out of the recycling and then test them in the bath (you're the judge), or create a scavenger hunt out of items you won't have to hide first. Things like that. Kids that age also tend to love helping so you could get them making their own lunches (I'm talking sandwiches not souffles) or creating their own pizzas for dinner.
I think you should be kind to yourself though. Not every day has to be about making memories, it's alright to put the TV on sometimes. And it's crap just now but these few months will barely be a minute in their memories when they look back in years to come. 