Hand me downs

My SILs have a 3yo boy and 17month old girl. They have been saving pretty much everything they could for my husband and I. I really couldn't be more grateful. We don't have a ton of money and are pretty new to the are so we don't know a lot of people. We will have 2 baby showers, one where we live now which will consist of his mom and sisters, and our neighbors (we live on a kick ass dead end, everyone is close) and the other will be where we are from with my mom and few old friends. I'm not expecting a lot of people at either shower and no one has a lot of money, so we're prepared to get the big stuff ourselves. All we will really need ($$$ items) that we won't be getting from his sisters are a car seat, stroller, swing and crib. I fell in love with a crib (4 in 1 converter) and it just went on sale so I want to jump on it. His sisters are telling us not to get anything until after the showers; and that they may buy a toddler bed for their son and could give us his crib (which also converts, so I'm not sure why they wouldn't just keep theirs). Honestly I don't want their crib now that I found the one I really like, and I'm nervous that sale won't last, or that it's on sale because it's being d/c and there won't be any left in a couple months. It would certainly save us $300 that we could use for lots of other things, and I don't want be stubborn or seem ungrateful, but on the other hand I don't mind spending $300 on something quality that will hopefully be my child's for many years. We decided to wait till I was 20 weeks to buy stuff, and I just hit 20w today. Now I'm getting anxious because we aren't ready at all yet and the time has gone by so quick. I don't know what to do. Any advice, please!