Baby blanket size query - what can I get away with :)

I have 2 balls of white yarn and a little pink and blue of the same yarn on cards from a kit that I bought years ago - its quite fine and I want to make a comforter/blanket out of it - just a small one for summer - kind of a carry cot cover.

What is the narrowest you guys think I can get away with?
Is there any way the yarn can go further (Magic? fairydust?)

I have no idea what yarn I’m using to buy more of it.

Am I being too ambitious?

When my kids were little I preferred 36 in square blankets. In summer a lighter weight blanket is fine, but larger is still better.

[b][color=indigo]Try doing a mitred square. You knit till you run out of yarn.

Using circular needles, CO 3
Row 1: K1 YO PM K1 PM YO K1
Row 2 and all even numbered rows: Knit across.
Row 3 and all odd numbered rows: Knit to marker. YO, slip marker, K1 slip marker, YO, knit to end.

Or this link may give you a better idea on how to do it.