It's a letter day, Moooooom.

I am a happy-to-be-homeschooling mom of two boys that are only 16 months apart. This age gap, while already considered a small one, shrinks every day. I started my oldest on some handwriting/letter practice - which I have to be careful with because he gets bored. His handwriting needs a lot of work, so I try to squeeze in what I can every school day.
I started my youngest on some color practice. He was working on the color green - and the instructions were to color a frog, a leaf, and a pod full of peas, green. Well, he balked. He argued. He refused. This was not his idea of a good time. He actually chose to sit by himself instead of completing his page. I try to always offer a choice - but neither of the options includes going and playing/watching tv/video game etc. It's usually school, or sitting by yourself. I'm not sure if this is the best way to go about it - but my youngest is very quick to give up if he thinks he's going to be doing something better than what's in front of him. It all confuses me, because he begs to do school.
I think I'm going to re-evaluate my system, and let him do a little bit more leading - because today, he wanted to work on letters. Once I got this through my thick "no, we are working on green right now" skull things went much smoother. We worked on every uppercase and lowercase letter of the alphabet, and all of the letter sounds! For him only being 3, I think that's a huge accomplishment! I have come to realize he really wants to read. He watches my oldest read, and he gets so excited. Once he realized that mastering the letters, and their sounds, was his key to unlocking the world of reading, he jumped on board!
My oldest worked on his handwriting, worked on reading practice, ate his lunch, and is now enjoying quiet time building with blocks. I feel guilty because I often think to myself, "Why is all of this so much easier with the older one??" - but I learn more from the younger one, and I am challenged to not just react to the frustration but to truly find a solution. It's not that either one of them likes to learn more, or is better at learning. They both are sponges, begging for information, soaking it up. The problem is usually the method. Who picks the method? Grr. Me.
I've also noticed that the fastest problem-causer is boredom. I should have thought about the fact that my youngest already knows what green is, and that frogs, spring leaves, and peas are green. I struggle with trying to balance review, with offering a wealth of new information and making it stick.

How do you balance review vs. boredom? How do you encourage your children to learn about the world around them?