I agree that drawn-out transitions are confusing and difficult. I think that shorter days/weeks could be okay in the beginning, but not long good-byes or staying on the first day. I'm actually surprised that the school would suggest this. You could ask his teacher(s) what they have observed as the most successful way to get started, they will have seen it over and over and may have tips that are particular to how they organize the day. Whatever your drop off routine and daily schedule becomes, you should be decisive and consistent from day 1 (open to change if it really doesn't go well of course).
Once your child is comfortable at school and confident on his own, you both may like it if there are opportunities for you to help out around school, thus bridging home/school/work life. My DS1 goes to a part time nursery school that requires parents to "take a shift" once every 8 weeks or so, and welcomes additional parent and sibling volunteer involvement. Not all schools allow this but it was an important reason I chose this preschool. Though it was a little weird for him at first, DS1 soon understood that mummy (with DS2 in tow) is there to work to help everyone at school and not to hang out with him in particular. We do our own things (he is building with blocks, while I am cleaning toilets down the hall ) but I don't shy away from giving him a squeeze from time to time, or doing other little things to let him know that I'm there and that we are connected. I really like that we can make school a family affair, that school/home/community are all integrated, and hope that I can find ways to carry this through as he goes on to "bigger kid school" in two years (a Montessori that is also cooperative in nature). It feels like a very natural extension of our AP approaches at home with the added benefit that it will make the transition easier for DS2 when it is his turn.
I hope all goes well next week! It will probably be easier for him than for you!