How long are these meals intended to last?
Under 40 minutes and all adults not drinking and their attention firmly on their DCs' table manners and making pleasant conversation with the children at the table - YANBU, children of that age ought to be able to sit still and interact nicely at table with adults for a short time.
3 hours long, adults eating their way through the menu and getting steadily inebriated, people telling the kids to buzz off and stop being annoying and the topic of conversation is Uncle Jimmy's latest bit of on the side and will she replace wife no.3, so you really don't want little ears listening in - YABU, it's probably quite useful to have the kids occupied with a game of Twister and trying to drive their remote-controlled cars up the wall even if it is a trip hazard.
If the in-laws book private rooms, then the kids aren't really disturbing other diners, are they? Though personally I'd make sure they were out of the waitresses' way so not causing them a nuisance.
Possibly the worst reason that you've given for your view is that you hate your 1yo seeing this. Very wet parenting imo, to blame your DC's behaviour on other kids, so you really don't want to go there. The other kids don't exist to set the example you would like to your child and "You do you" (or in this case "your kids") is usually a good attitude to take to parenting.
Ultimately if you don't enjoy the meals, don't go.