is two days in advance ok for a cake order, can i do it on sunday if it's to be delivered on tuesday??

Yes, you can do it on Sunday for a Tuesday delivery. Whether 2 days in advance is enough time is up to you.

Only thing in my kitchen that gets less than a full week notice is a cupcake order. All cake orders need to be at least a week in advance (paid in full at booking) and all wedding cake orders need to be 4 weeks in advance (also paid in full). More notice lets them pay half down and half on that time schedule but those are my minimums.