To prefer that my kids were adopted by anyone BUT my inlaws in the event of my death?

[whomovedmychocolate]

Am currently on holiday with MiL, DH and DD (hotel has wireless so have snuck away). We stayed with SiL last night and DH (quite undiplomatically while I wasn't around, told SiL - she would NOT be named as legal guardian in the event of both of us dying because she is too old.
She went flipping mental and was still going on about it three hours later when we had dinner, wherein I tried to calm things by pointing out that she is 50-something now and she may not want to inherit a 13 year old when she is in her 60s, that as I am 20 yrs younger it'd probably never come up and that social services would have to assess her suitability if it did and that perhaps my brother and his wife (my age, three kids) might appear a better fit.
At which point MiL (80) pipes up 'well if it happens we would FIGHT for her'. SiL agrees and says 'I'm sure I could convince a court I was suitable if I hire a good barrister'.
When I responded that my daughter is not an object or prize to be wrestled for they said 'well it won't be of your concern - you'll be dead'!
DH and I discussed it later that night and as soon as we get back we are appointing two sets of guardians and making sure DD is protected from all this.
Would you leave your daughter in the care of these self-obsessed harridans? Not to mention any future children we might have.
I'm so angry with both of them.

I was told that if you don't allocate someone and you both die, then they work out who died last and give your dc to their parents.
The thought of me dieing first and my MIL getting 'control' of my dd terrifies me. However my dh feels the same way he'd hate for my dm to get our dd so we've been struggling to think of someone (we each think the others family is barking). our godmother and 'ungodfather' (Athesist, but lovely man) would have been our first choice, but have made jokes about not looking after her.

Whomovedmychocolate: not unreasonable but agree with others you must get something down on 'legal' paper that should stop the cheeky madams.

I have found a good online guide to what happpens
here

It's difficult isn't it though. My parents are great with my kids but they are 76 and find them trying for long periods. My brother lives in N Wales so they'd have to move and lose all their contacts and their home which would be double hard on top of losing their parents. We asked some good friends of ours but they'd already agreed to do the same for her sister's 4 kids. So atm my parents are it but the older they get the more problematic it becomes.

and from a social services/benefits PoV read this