WIBTA for bringing a fake boyfriend to my friend's party?

to condense as best i can, i (30, transwoman, city of pop. >10million) recently become the mother hen to a brood of wonderful baby queers (8 total, 17-23, boys and girls, all moved for school in the last year or so, most had never set foot in ANY city before). we live on the same floor of an apartment complex, and we've all grown very close over the past months; i help them use the metro, they tell me when they're going on dates and text so i know they got home safe, i cook weekend dinners, and they all slept in my living room for a week when another apartment on the floor was broken into. i think of them as somewhere between friends, younger relatives, or even my own children.

recently, one of the older ones (21) has realized he's also trans and come out to me, and i'm so proud and grateful that i can guide him through his early transition. unfortunately, there's his mother.

he'd first told me her response to his coming out was "better than expected", so i assumed she was tolerant, if not supportive yet. i've since learned she continually misgenders him, thinks this is a "tomboy phase" he'll marry out of someday, and has begun listening to more right-wing podcasts and news sites in order to "hear from both sides".

along with the other 7 kids, i've been invited to stay at the family's farm for his birthday in august, & while he's assured me she won't make a scene with company around, he's implied she has many opinions about my prescense, but said that i shouldn't tone myself down, and that if anything "it would be good for her to learn to be kind to you early, since we're family too now". two of the girls are partners, which the mother knows, but she does not seem to care about this and said that bringing a date was fine.

i have another friend (31) who's much more loudly queer than i am. on top of this, he's heavily tattooed (HUGE taboo here), rides a motorcycle, and is very outspoken and unshakable. i told him about all of this, and he offered to come along as my boyfriend, both to bother this woman, and so i won't be in a tiny (population SEVENTY-THREE!) unfamiliar town alone if anything happens. he's met the kids several times now, they get along well, and the birthday boy has said "that all sounds hysterical. do whatever you want."

my worry here is that the mother is already MUCH worse than he'd first lead me to believe, so i don't know that i can trust the kid's judgment that everything will be fine. i don't care about hurting this woman at all, and both i and my friend have dealt with even nastier people before so i'm not afraid of her, but i DO NOT want to do anything that could put this boy in a difficult position, especially since he'll likely be living with his family every summer until he's finished school, if not longer. i know what i can personally tolerate, but i don't know what he can, especially from a mother.

would i be an asshole to bring my "boyfriend" along? is it best to just go solo? or should i stay away entirely until he's back in the city?

What are these acronyms?