I do cirlcle with my group, they love it and have no problem sitting through it. Although it`s not all sitting, I break it up so we stretch and they also participate. They get to take turns putting the date on the calendar and the weather stickers. We do a couple of the same songs everyday (Oh Canada, Good morning, the more we get together) and some different ones depending on our Theme.
I usually plan my Themes a few months in advance but I don`t do one for every week, I do monthly (and break them up into mini themes). For example I might do community helpers and spend a week talking about emergency workers (police, ambulance, fire fighters) with a trip to the fire station that week. Next week talk about Farmers with a trip to the Farm and then talk about Doctors, nurses and Dentists and the last week talk about all the other CHs like Teachers and Postal workers. I pre order any books I want online from the library so I can just walk in and pick them up and not search for them. I print off work sheets and coloring pages and organize craft ideas the month before. I work letters, numbers, colors and shapes in all our Themes, ie. F is for Firefighter. The truck is red and cut out rectangles, squares and circles put together to make a Fire truck. etc
I don`t know where you live but our libraries have some theme kits that they lend out.