Easy to set up (and clear up) activities for 21 month old?

Books, websites, your ideas all very welcome. I need to entertain my toddler while I nurse her little sister and want to start preparing/collecting/buying stuff before her Dad goes back to work.

Best activities are toddler only but stuff I can help with in a limited way while breastfeeding are also welcome.

So far I’ve allowed her to draw on a table I dont care about and created a play corner in the lounge (which she doesn’t seem to use that much now it isn’t toys scattered everywhere).