RP from SAHM boards... Thanksgiving WWYD???

O.k. so MIL has gone on this extreme homeopath diet (long story - kinda peeved to say the least about the whole thing - she thinks she's got a bladder infection that won't go away and refuses to go to the doctor to even just get it diagnosed but instead is seeing a homeopath who eliminated all fruits and wheat/gluten from her diet amongst who knows what else - she doesn't even make it to a "Dr. Google" diagnosis - she just gives herself a diagnosis without the slightest bit of education on a particular problem)... I digress... So DH stopped over at her place and asked if there were any requests that she had for Thanksgiving (we're going over to SIL's)... SIL has Celiac's.. MIL requested Pumpkin Pie... Not a big deal but I pointed out the obvious "Um - pie crust contains wheat/gluten.. but that I'd make it without the crust or ginger (since I'm allergic to ginger) so none of the three of us wouldn't be able to eat it..." Well, fast forward, SIL was at the grocery store and they had a "deal" on buy two pumpkin pies and bought two today... The thing is, I can't have it because of the ginger nor can SIL or MIL because of the gluten, and DH - well he just hates Pumpkin...

What would you do??? Would you make the crustless pie (was goin to put it into custard cups and bake it that way), follow SIL's wishes to not make it since she bought pumpkin pies already that at least four of the 10 people coming won't be able to eat, or follow the MIL's wish of being able to have Pumpkin Pie for Thanksgiving dinner even if she didn't realize that no wheat/gluten means no regular pumpkin pie..  I should also add that SIL is one to complain about having to "do it all herself" but of course, when you ask there's nothing she wants me to bring and instead to be there on time/long before things start and doesn't want help then either...