Decent inch sized crack in sidewall. Slowly leaking air (fill up every couple days).

I have 4 new tires coming in two days to get installed at Sam’s Club but I’m afraid of a blowout before then.

Should I just go to a local tire shop and get a replacement asap like today? I don’t want to buy a new tire that has new tread when the 3 other tires have about 25-50% life left. Should I just nut up and install all the new tires and keep the used as spares?

Regardless, I feel like I need to do something about this today to avoid a blowout but I’m afraid of wasting $$$ because I have the new tires coming Thursday.

Any advice? I do have a full size spare I could install in the meantime. What do yall think? Just strapped for cash this month and trying to be as smart as I can about this and not waste tires and $$$.