You are very dillusional if you think you can get a family member to step in! It doesn't work like that you can't have random people in and out ofsted will close you down.
You say your going to have 48 children under 3 so we'll split the difference then
24 0-2 year olds need 8 staff, half of which (4) need specific baby training so 0-36 training, at least one will need to be level three at all times and at least four will need to hold a level 2 at all times. You will need a space of 84 m2 for these babies
24 2 year olds- your going to need 6 staff 1 whose a level 3 (and no not the same level 3 person you have for the babies a different one) and at least 3 level 2 staff. You will need to ensure that you have 2 year old check system in place for these chcildren you will need 60m2 for these children.
So in total 144 m2 of useable space for your children also, this doesn't mean space they can't access like hallways etc it means space they are using every day like a giant hall !!
Also before you say it you can have a ratio of 1:13 because your a teacher as this only applies to children over three and your not having children over three remember.
www.foundationyears.org.uk/files/2017/03/EYFS_STATUTORY_FRAMEWORK_2017.pdf
This is statutory guidance maybe read it since you have no clue about it.
This is what is in the legally binding statutory requirements and this needs to be maintained even through breaks, sickness annual leave etc you can't just put someone else in there to cover