Safe Child Car Seats Safety Car Seats For Your Child

Just want a few opinions on a pre used car seat?? Its a long ?

Ok my BIL/SIL want to give me there son's old car seat. But I want to know how I could stress to them..(without) hurting there feelings, as I want to get my son a new car seat. Its a cosco Serena car seat from walmart.

Cons.
1. It's been in there attic and wasn't cleaned or covered up prior to storing it there. So I don't know about how the heat would warp the plastic etc
2. It only goes up to 40lbs. I would like something up to 50lbs.
3. When it was installed in there car. I always remember it being overly wobbly and I dont remember seeing them checking the seat belt to see if it's not to loose. Bc sometimes we would ride with them places while I was pregnant and I had to sit by my nephew.
4. I don't think it comes with L A T C H system
5. Made in 03 or 04 and doesn't have Side Impact Testing..
6. I dunno even if it would fit correctly in our car bc its small and they drive a Jeep Grand Cheorkee..2005

Pros.
1. Would only save us about 50 bucks
2. The cosco seat they've got hasnt been in an accident tho..

Don't get my wrong I love them to death, but my husband and I would like to try and save money by buying a good 3 in 1 seat or at least a better convertible seat then get a cosco booster seat later on.We decided to see around tax time to get a seat. So it wouldnt really take out of our budget. The other reason is I would like something that keeps him in 5 point harness longer(and has SIP) bc there son is already in a booster and KNOWS how to un buckle himself while they are driving or have the car stopped but still running. Im not trying to judge ive seen both these incidents with my own eyes. Hes a bit of a wild kid and Ive heard both his parents say this themselves. I dont want to seem like their bad parents, bc they're not. I know that with somethings they let there son do or say..I wouldn't with mine. I just want something a little safer and in date. Whatever seat we chose if it stays in good condition I would like to save it for our next child..depending on when it comes.
I wasnt really worried about the dirty part. I could scrub to no end to clean it. I was worried about the safety aspect of the seat. No we only have one car, but I really wish we had a van. Gosh does a baby ever take up some room! ah but I love him any way..