Travel equipment

We’re taking our almost 5 month old abroad next month and I’ve been looking into the rules around what we can check in for free and how much we may need to pay extra. Flying with Jet2 and I’ve just read we can check in a car seat, travel cot and pram for free as long as it’s a combined weight of 10kg which is pretty much impossible… the car seat is around 3kg, travel cot and pram are both around 9/10kg each! What’s anyone else’s experience with this? If you are taking the pram right to the plane do they weigh it at the bag check in beforehand? Or do they just weigh what you are checking in with the suitcases? Are they really strict about the 10kg limit and how much extra do they charge when you go over that? I remember once being charged like £10 extra per kg for an overweight suitcase before Any insights would be great thanks!