Pre School hours

My little one starts pre school this Sept. He will be 3. He is used to other kids, he goes to a childcare setting currently 3 days a week part time. I’m expecting my 2nd child next month. My question is I need to choose how many days/ hours to send my 3 year old be it 9 to 1 or 1 to 3.30 or the full day 9 to 3.30 I am currently on maternity leave from work so will be at home for 80% of the academic year with the new born baby. I do get help from mom (have to pay her mind you) and dad (he don’t charge me) they are separated so help me on different days when needed once a week usually when I was working but now I am on maternity leave so have their help sporadically when I have appointments doctors / hospitals etc or if needed. Do I send him the full 5 days or not. I’m thinking to send him 4 days possibly. It is literally at the bottom of our road so just a two minute walk to get there. Does anyone have any suggestions for me? I feel bad as I will be off work on maternity at home anyway so maybe I shouldn’t send him that amount of time? But then I don’t know how it will be with the newborn baby too and starting back at work the following year in June on a part time 30 hour a week contract over 5 days. I need to make a decision 🤷🏻‍♀️