I would bow out gracefully, still talk to the ones that don't do that. The ones that are doing it will not notice anyway. I would let it go. But not put my children or myself in that position to be hurt.
what exactly are your children missing out on anyway? they have their grandparents on both sides to shower them with love. you do have feelings of jealousy, but i have found that it is usually rooted in something more. you have not confronted anyone so how can they be expected to change when they don't even know that there is a problem. or that they don't realize what they did. and your children are not lacking in affection or attention, then basically you are mad because you have been snubbed and your children have been snubbed, or you are not as important as you thought...because your kids deserve the same as the others.... and that you are not as close to some of these people as you thought. and that is probably is what has your dander in an uproar.
my mother-in-law has always treated my nephew as her favorite. me and my husband were a couple, expecting and planning the wedding. his sister got married about 3 months before us. we had our son, the first grandson. then she got pregnant when mine was 9mos old. and i was pregnant again also. so my middle son and her first were born two weeks apart. then i had a third, and three months later her second was born. Each time I have invited my MIL to come and help with the babies. But of course she can't because she has to help her daughter. All my nephews and now niece (of coarse she had to have 3 kids because I have 3 kids), are all by different daddy's and she is on her third marriage (of coarse she had to have the only girl).(I told my husband I think she is trying to be me or compete with me, because she has since gone to nursing school to be an LVN and you guessed, i am an RN, everything i do she either does it first or copies me). her kids get more attention, time, and presents. i finally just had to let it go. my SIL lives closer, daughters are generally closer to their mothers(?), and she acutally does need more help than me. It did make me mad for a long time that MIL saw her other grandsons all the time but couldn't visit us on her own to get to know my sons. she would always bring nephews on visits to us. They always monopolized her time while with us and my kids still didn't get to know her because she always had my nephews with her. or she couldn't come visit because she had to babysit a kid for part of the summer etc. But she never offers for my kids to come visit for 2 weeks or even a day, but she will keep my nephews all the time during the summer. I am nice to her when i see her, but i don't go out of my way. i invite her to our house whether she brings my nephews/neice(whom i do love) or not. she usually doesn't visit anyway. we have been married 13 years and she has been her maybe 4 or 5 times. so the average is with me, that i can tolerate her bahavior for a short amount of time. when we go there i just make sure to keep the kids entertained, i do take my nephews where we go, like to the park for a while. and just come back home. i have just come to the conclusion that we are just not close to that side of the family. i take it for what it is. and work within those guidelines. when i stopped expecting more, or different i was able to let it go.
the anger comes from wanting it to be one way, or expecting it to be one way, or operating under the assumption that it was one way......and you found out otherwise and you feel betrayed or snubbed.
i always thought a grandmother should do x,y,z. and when my MIL didn't i got mad. or when she showed favoritism. what didn't occur to me, that my cousin can say the same about me and my grandmother and my boys. we live closer, i have 3, she only has 1. i visit my grandmother all the time, and she doesn't. but again i am closer to my grandmother than she is. and my grandmother doesn't snub her, granny is just old and can't travel as much. but she babysits for me more, because i live closer. etc. then i realized that my husband is his grandparents favorites. His grandmother always said my third son, was "her boy" because he reminded her of my hubby when small. because his grandparents helped raise him. and what ever 3rd son wanted he got. 2nd son is his great grandfathers fav, because he is named after him. my oldest is my dad's favorite, his first grandson and he helped babysit him alot while a baby before second son born. they all still love all the kids, but feel a special connection to one or the other, or get along better with one or another. i think is is just natural.
so, foster the relationships that are close to your kids, let the others go. don't go out of your way to be mean, don't cause strife either. but don't go out of your way to visit the people who do these things. invest more in the people that are closest to you. and realize those other people aren't that close to you. i would go to family functions with no expectations. i would only sit or talk to the people like your in-laws, that pay attention to you and your kids. and when the others approached i would talk, and if they didn't come to me then i would leave them alone. i wouldn't approach them, i would just wait for them to approach me. if they didn't then oh well. if anyone asked i would tell them nothing is wrong. i'm just not as close to that group as i am my MIL or FIL. i would still have a good time seeing the people that mattered to me. but if the others don't want to talk to me than they are missing out. you can't make people want to hold your baby, or give attention to your kids. and you can't possible be close to everyone in his entire family.
some of these things are just human nature. and all ebb and flow. and realize that somewhere what you are saying about them, someone is saying about you.
and are all of these people that important to you? they can't possibley be? all of them, that you would be so offended. It's not like your MIL did it? or your own mother?
let it go. and rise above it. i can't make my MIL be any closer to my kids than to offer her the chance. If is her choice to take it or not.
I like the quote that the road travels two ways. that is a good quote and very good advice.