You might want to remind your mother of your own childhood interests, and you turned out straight.
Your mother and mother in law are a bit of a concern. Considering how INCREDIBLY DIFFICULT it is to get kids to pick up their socks off the floor, put their dishes in the sink, hurry up for the school bus, it seems unbelievable that with the mere suggestion of toys offered, we could change their whole sexuality.
I am usually a "go with the flow" type of person, but I think you need to make a strong stand here. Your daughter is who she is.
As an example, you might want to bring up Chastity/Chaz Bono. There was never a girl who was dressed in more girly silly frilly dresses, named this silly girly name of Chastity, and look how that turned out.
Um hmm.
Your gut instincts are right. They need to butt out and let your child play with whatever she wants.
Do they really want her to learn to pretend to be someone she's not? Do they want her to do stuff and like stuff just because her peers do it and society expects her to? If a child internalizes those messages, think of the things she will do as a rebellious teen.
If I were you, I would foster her natural interests. It sounds like she's on track to become an architect ;) Of course, it can't hurt to continue to introduce and expose her to other things, including "girly" things. But it can be very harmful to make her feel ashamed of her interests.
And every kid who uses a toy gun will grow up to be a mass murderer? Outside of the fact that your relatives really have no clue what "gay" means, its kind of sad that they want to push her into their life style. But, thats what comfort levels are about I suppose.
Anyway, toys are (hopefully) things that you play with friends, and not by yourself cause you have no friends. The toys you thus play with reflect who you are playing with. And as far as I know, a girl playing with boys will not encourage her to be gay. Later on - yeh, there might be other things to worry about (and it won't be gayness).