If you are blessed to have family members who care enough about you and your children to give loving advice that's a great thing! However, sometimes their advice can be outdated or just completely wrong so you need to beware. It might put you in an awkward position with the in laws, but you are a mama now, a grown woman who can respectably decline unwanted advice.
1.) "Just give him/her a bit of honey"
Absolutely No Honey for babies under 1. I have had my mother and mother in law tell me to give my baby honey. They meant well, but that is some dangerous advice. This can cause paralysis in your baby so just don't do it!
2)" Cover the car seat with a blanket for the sun"
Do not overheat your baby. We all know not to leave our sleeping babies in the car to visit the store but did you also know that putting a heavy blanket over your child's car seat can also lead to suffocation or in most cases heat rashes? The car seat is extremely warm so a light muslin blanket if any is usually sufficient. You need to keep in mind small babies cannot sweat so they actually feel warmer than you do if there is no wind.
3) "Your baby needs a blanket to sleep or they will be cold"
There is no need to put a blanket on your baby if they are wearing a sleep sack (sleeping bag) for the correct season. These things are blankets already that just don't look like regular blankets. The fact is regular blankets can be extremely dangerous for a baby if they are sleeping on their backs. You have to keep in mind the sudden movements babies make in their sleep and the fact that they like their arms up.
4) "You need to give your baby water"
You do not need to give your baby water under 6 months especially not one under a month. They need to get all the nutrients possible from the breastmilk or formula. Plus these things are made up of mostly water.
5) "Your baby is not fat enough, you have to feed him/her more".
Do not force feed you baby. Your pediatrician will check your baby's weight and determine if they are indeed underweight and what steps you should take if any. Some babies are bigger and some are smaller, there is no need to make your baby over weight so someone can think they look cuter.
That's all I've got for you guys today but you can definitely add to the list in the comment section.