I pulled my 3 year old son out of pre-school, mostly 8:30-12:15 mon-fri, but I never made it all those days and I wish this awesome Montessori School had just a one day a week fee! That would be something I would look into now even, but just to clean the house. After my daughter had grown out of a really TLC colic acid relux stage, it was heavy on my mind why I was sending him there. I found I just could not give him enough play attention when she was so fragile, but not after about April. You want to do what is best for her and your baby? Would you think about keeping her home and creating your own school with her? Or is this time she goes something you need for yourself or your income? If it is all about her, than I would surely keep her home much longer and simply pull the plug on the TV, or at least keep some videos when you have to put the baby down for a nap that are about letters. Try to sketch out the day as best as you can or week too, and try to stick to that plan. I think the routine that they have at the schools is a real product worth buying for our own children (and I am having the hardest time giving it :), but I make it most days!)
I am still working on a reading list for my son too. But I am just sticking to the home routines and taking care of himself. He can do tons now but it took a lot of patience. Get himself dressed, make bed, brush teeth, wash hands, set the table, pour tea, and even make eggs :). He and I read tons of books while his sister naps and he is beginning to write lots of letters. The best, best, best part is! He and his sister are beginning to play together!
I vote let her stay there for three hours while you take the baby grocery shopping - that realllly helps! She will look forward to it very soon. If you are really looking at the cost of this arrangement for getting groceries with a little more focus, then yes, let your DH watch the kids on the weekend while you go or all go together and teach her something about shopping. :)
I hope this was helpful! I had to do a lot of soul searching to finally give in after umm, Nov-Jun of sending my kid to a pre-school... every morning he missed me and once in a blue moon he was excited to go. Mostly though, he wanted to have what I described above and I love it too! We go on outings as well.