Wait, are people saying that they don't feel the OP's kids were safe with the XSIL because she's deaf? Maybe they were uncomfortable because they didn't have an easy way of communicating with her (but with phones and pen/paper they obviously could), but assuming she has her license and is allowed to be driving her being deaf does not mean the kids weren't safe.
If a kid needed a bathroom, say, while XSIL was driving, you couldn't really text her or slip her a piece of paper while she'd driving. The reverse isn't great either, when my aunt used to drive us sometimes and there was a baseball game on, my one cousin would demand that her mom give her the play-by-play. This was the oral-school cousin who lip read exclusively at the time.
You could tap them on the shoulder and cross your legs and make the universal sign for having to go to the bathroom. So again maybe not a super easy way to communicate but that doesn't mean the kids aren't safe.
I would let this go with the xSIL. The kids went mini golfing, got fed and got Starbucks (not what they liked but she tried). She took care of them and tried to plan a fun day with them.
Just tell your FIL to let you know next time. If the kids are in his care, he needs to let you and your H know if they will be going with someone else. You should be mad at him. But to be fair, he probably thought the time with xSIL would be more fun for them. I am not sure I understand the communication issue. Was your FIL worried they were gone so long? If so, did he text the xSIL? I understand she's deaf but she's not blind. She can read texts.
I'm sorry, perhaps I wasn't clear. Both my cousins drive, and I have been a passenger in their cars a couple of times. (They live 300 miles away and we don't see them as much since our parents not all still with us) It's fine. My concern is not specifically that the XSIL is deaf, but that communicating with a person who is deaf while they're driving is not safe.
If a kid needed a bathroom, say, while XSIL was driving, you couldn't really text her or slip her a piece of paper while she'd driving. The reverse isn't great either, when my aunt used to drive us sometimes and there was a baseball game on, my one cousin would demand that her mom give her the play-by-play. This was the oral-school cousin who lip read exclusively at the time.
It sounds like there are numerous hard of hearing family members, I'm sure that if the child didn't know how to sign that they needed to go to the bathroom they'd be able to figure out how to google it. The kids lived with the XSIL for a year, she may feel closer to the kids than they feel to her and she's trying to rebuild the relationship. Or she's a selfish asshole who was carting the kids all over and not caring if they were having fun. Either way, I don't think her being deaf is a danger at all. ASL isn't that hard to pick up and it'd probably make sense for the kids to learn some if they'll be spending any time w/their extended family.
Yeah this is where DH and I are - she likes to do things for the show of it, for the accolades, and for her own benefit. Our kids were just props and a reason to leave the house for her. I'm surprised she didn't post pictures of them out and about on FB saying what a good time they had, because in the past she absolutely would have.
I fully admit she is BEC for me in a lot of ways - but it's not without past experience of her antics fueling it.
FWIW, we would be totally fine with either of my Deaf BILs taking the kids out on the town for a fun time because we know they actually have a good relationship with our kids.
Either way - we're over it, the kids are fine and know what to do next time, and she'll never get the chance to take them anywhere again.