Okay...number one...You are doing just fine! Answer the questions that come up to the best of your ability and you are rock and roll! In my opinion, what kids need to learn at this point is how to navigate their world appropriately...the rest is icing.
Number two...If your kids (and you) are into writing or table work and so on then great but if not, there is NO sense in pushing it. Doing too much too soon may not be good for them (if it is intrinsic then great but otherwise, no sense in pushing it). Forcing them to do it now will make them less enthused in the future.
AND learning to read and write doesn't have to happen at a table! tracing letters in the sandbox is equally good if not better.
questions to ask along the way (that you probably ask if not answer already):
What color are the leaves on your walk? What colors do you see on your walk? Can you find the letter A in this aisle of the supermarket? If you were a superhero what would your super power be? (that is by far my favorite line of questioning) What does a mailperson do? How many bugs is that? Can you hop on one foot? How many apples? First we spray the water and vinegar, then we wipe it with the rag. We are going to take turn with your sister? How does that make you feel? Why do YOU think the sky is blue? What is your favorite ____? Is it a square or a rectangle?
The real question is...are you doing your 3yr old's preschool.
If not, then leave the crafts and circle time and all that to the preschool and allow your child to be a child (if you are nervous about what people will say, then read up on overscheduling children, the importance of imagination and letting children play and a physical relationship with their environment and game over).
If you are doing their preschool, then know that in order to be considered academically ready for Kindergarten they need to be able to sit for some time (you can accomplish this when she is 4 and your little one is 2), know shapes, colors, letters, numbers, count to twenty...I bet they know most of this stuff already.
Table work is one way to do this but not the only. You can work fine motor skills in the sandbox, kitchen, anywhere.
The key to crafts is having everything out before they come to the table...easier said then done! But you don't have to do this either. (If guilt overcomes you look at Frobel's gifts and use or adapt them as you see fit.) But it doesn't sound like either of you are into table work kinds of things...and of ALL this things in this world to fight 3yr old with...really, does macaroni necklaces have to be top of the list?
Creativity doesn't come from sitting at a table with colored pasta, it comes books and allowing the mind to unfold and explore. There is a lot to be said for a naturalistic approach.
If you want to work fine motor skills you can do by having her do things around the house. But also, you may want to go large bolts and nuts to screw on and off, scissors and put a bunch of recycling (or bank statements ^_^) in a bin and let her cut cut cut. Playdoh is a good thing but making cookies, biscuits and bread is too!
number three...other moms are creating a world in which they can coexist in happy harmony with their children. You are doing the same it just doesn't look like their model...it looks like the one that fits your house...as it should be.
And finally (promise) number four...My kids are the same ages as yours. It is very VERY difficult to do something focused with both at the same time. When they are both awake, I am trying to keep everyone alive! I try to set aside 10 minutes every hour to sit on the floor and read a book, play a game, etc (some days are better than others!) but I ask questions throughout the day as they come up. I also have them help me through out the house...the one year old pulls the clothes out the dryer into the basket (and then onto the floor) while the 3yr old helps me sort the clothes. I put more focus on getting everyone to help me in the kitchen then I do on setting up a sensory table. For example before we sweep the floor, we make biscuits and the 1 year old gets flour and raisins or yogurt and something in a bowl with a spoon and the 3yr old mixes, pats, and plunges the biscuit cutter (the last little scraps he makes into an animal with raisin eyes). I'm not going to lie, some days we eat the biscuits because they are there but most times they taste fine. My son happens to like table work and is eager to read books on his own but some days he just isn't into it so we don't. I can say I very much doubt my daughter will be as diligent in which case we will take a different approach that will suit her.
I have learned that to be able to focus on the things that my son wants to learn (like complex books, writing, sight words, gluing cutting, etc) my 1yr old MUST be asleep. In our house it works as a symbiotic relationship: He is quietly working, she is sleeping, I am writing a post! When my 1yr old is up, we do gross motor (balance beam, cleaning, playground).
In my opinion it is more important to have structure to the day (which it looks like you have) then structured activities.
Hope that helps...if you want easy craft ideas, email me...