I read most of the posts here but thought I'd give my 2 cents.
We do a lot of free play but in the morning when the babes are napping we do our activity time. We start with reading for 20 minutes(each kid picks a book or 2) and that time gives the babes some quiet so that they can fall asleep. By that time they are passed out and we can chat it up
Our activity usually has an educational element but i look for things that take very little prep. Yesterday i wrote M is for...and they colored(mountains, monkeys, mommies). This helps my 3 year old recognize letters and my 5 year old year with the phonetics and our 2 year old is on his own planet but i know he will pick things up later.
In the afternoon we do sensory play ( ie making cookies, making play doh and playing with it, a bin sith colored rice and baking items, stuff around my house)
All these things make me the happiest because i feel like i accomplished something that day and the kids usually like each other better by the end of the day.