With my DS, there's no way I could bring him to a funeral. He's a well behaved little thing, but being a well behaved 13 month old appears to involve launging, blowing rasberries, running around, trying to open and close doors, pulling things off shelves, chewing people's keys (and occasionally shoes), waving and saying "hi" to people, animals and friendly looking furniture and doing a whole bunch of perfectly normal things which unfortunately would not go down well at a funeral ...

and as he's not being naughty and just doesn't understand that it's often a sad and solemn occasion (though sometimes is a loud and lively celebration) I don't want to be trying the whole time to make him shush and sit down quietly.

At AGMs and church sermons and other things where generally people keep quiet, I often will take him, and when he's hit his "playing quietly" limit either DH or I will take him elsewhere.

But if there's no simple option for "elsewhere" I would either find a babysitter or just stay home with him.

Or possibly find somewhere nearby and warm where I can wait it out, and then go with him to the wake to support your SIL and hubby. Even if it's just a nearby Maccas where I can grab a coffee and let DS play on the equipment for the hour.