We're talking 25m here so don't suggest anything too sensible please like sitting still and doing a jigsaw - DD1 can be happy for a while watching CBeebies but gets fed up just as DD2 is falling asleep and crashes into the bedroom yelling sisterly greetings.
I take them both out whenever possible but for lots of reasons can't do this for all DD2's naps.
DD1 used to sleep while I settled DD2 for her long nap but those days seem to be ending ...