I think it's great that you're thinking about teaching your twins and considering various parts to doing it. I like the Montessori method, the little about it I know, anyway. I suggest that you don't need to do formal home schooling. Just being aware of how you want your twins to learn and finding some materials to use is enough. Many children enter kindergarten without having been to preschool. I'm guessing that most of them have a start on learning numbers, colors, the ABCs but some don't. In my granddaughter's kindergarten class there were students who could neatly print their name. But most of them scrawled their name in large uneven letters. She praised everyone of them, even those whose name was not legible. She then taped each name that they had written to their assigned desk.
The teacher told us that it was not important that students know certain things when they started kindergarten. What was important is that they had been exposed to the basics. She also said some children are not ready to learn any of what we seem to expect them to know at age 5 until they're older. Some things, like printing, they're not able to do neatly until several grades later. So much of what we learn is dependent on both physical and emotional maturation as well as exposure.
My granddaughter was in preschool from the time that she was 3. At 3 they did very little formal teaching. They spent more classroom time at 4 but still the focus was on providing toys/objects for them to learn informally. One of the important learning opportunities for many was how to get along with other children and in a somewhat more structured setting.
You can do this without having any teaching experience or formal material. You've been teaching your twins already. I think Montessori emphasizes learning opportunities. My daughter was in a Montessori Summer school after the first grade. The room didn't seem too different from any other large day care to me. The room was organized and contained many different sorts of opportunities. I worked full time and didn't take the opportunity to observe. I do know that they had a lot of free play time and that it didn't seem that they taught "standard"academic subjects such as numbers, alphabet, colors. For my daughter the focus was on learning how to get along with others and increasing her sense of security and self-confidence.
Your twins will learn from any experiences that you give them. Going to the zoo, the Childrens Museum, the Science Museum, having play dates with others their age, Playing with dried beans, water, clay, anything to encourage sensory awareness. Having crayons, markers, paint, paper of different colors and textures. Putting together blocks. Playing make believe with anything available. A box can be a house, a store, a boat.
My grandson is in a home day care/preschool. She purchased curriculum from the state. It felt mostly like craft projects with a learning focus. They did work sheets (how boring). Cut out objects from colored paper. This seemed fun. Drew pictures. The curriculum provided for 1 hour of instruction/day. Each day, the child had something to take home.
My grandson was in a half day therapeutic preschool at the time. He did sometimes have something to bring home but not most days. Their focus was more on play and learning thru play. Many 4 yo's are unable to sit and do something. My grandson did not fit in a regular preschool with a classroom size of 20 and 2 teachers and a couple of aides Home schooling is a wonderful way to go. You can provide personalized learning opportunities.
My grandson has never liked work book type learning. My granddaughter didn't like work books until she was in the first grade. The school that she attends uses a lot of black and white work sheets and she seems to find them boring. I bought several colorful and fun looking work books from Fred Meyers and The Learning Palace because I had enjoyed them as a child. My granddaughter worked on them while we were driving or at a restaurant but wasn't interested in them any other time.
I think it's especially important to not have a set schedule but to provide experiences based on what else is happening at home. Be sure to allow yourself to only do what you're able to do on any given day. Be careful to not set all of you up for a sense of frustration or failure because you weren't able to accomplish certain goals. I hope that you can mostly relax and have fun with your children. You are their best teacher just by being their mother who is interested in their learning.
I think it's often easier to teach when there are two children. They will learn from each other. They excite each others imagination. You can have them both coloring or playing at the same time or if one doesn't want to do what the other one wants to do have them each doing something different. One can be playing alone while the other is doing something with you. It should all be informal and manageable from your view point. You don't need to do anything difficult. Just being aware that you want your twins to have various experiences and then providing them is a good preschool experience.