DH and I both have life insurance that will cover funeral expenses, with money left over. We're both organ donors, have wills, living wills, and health care power of attorneys. We've discussed what we would do/like to have done if one of us were to die. DH knows I would prefer to be cremated and would have him cremated, if something were to happen to him first.
I've also discussed my Mom's wishes with her. She's only in her 50s, so I think she'll be around for a long time still, but she would prefer to have side-by-side plots with her DH in the local Catholic cemetary, someplace away from the road. I told her I'd have an angel engraved on her headstone since she loves angels. She and her DH have life insurance, as well.
I'm not certain what my Dad's wishes are for when he passes, but I'm sure he has life insurance and that his wife knows his wishes. As long as I'm invited to any memorial service or funeral for him, I'm fine with whatever plans are made.
I have no idea what the ILs plans are regarding their deaths or whether they have insurance. However, they all have enough assets that their estates should be able to cover the costs of funerals and DH and his brothers see eye-to-eye enough that they should be able to agree on arrangements.
Regarding the DISer referenced, I too would be upset if someone spent money on funeral arrangements for a family member, without asking how much I could contribute, and then TOLD me how much money they expected me to pay. It's one thing if I'm given a phone call and told, "There's no life insurance. Could you pay $1000 toward the expenses?" up front and another when you're given a bill after the fact.