Hi and congrats on your pregnancy!
My dh was born in India and raised there, and I was born/raised here and am light skinned. We have two daughters. Although dh and I went through a religious phase early in our marriage, I would say that we are not that religious now. Dh and I still will do an occasional puja in our home but we don't go to temple very often at all-- maybe twice a year he will take them. I feel that my kids are a good mix of both of us. They do not speak his native Tamil.
I am sorry you feel resentment about your parent pushing you so much. I have seen this in friends who were born here, parents from India, who were raised with Hindu culture kinda shoved down their throats but little explanation into the meanings of things. Or they have converted from Hinduism to Christianity, or are just searching but they know they are not Hindu like their parents. You don't necessarily have to be settled on what you believe or don't believe to raise a child who can be open-minded about both sides of their heritage.
Maybe for the baby ceremony, ask your mom what elements are the most important for her as the future grandmother. You can pick and choose a couple of things-- like wear clothing that is comfortable to you, but maybe a dupatta wrapped around a nice dress or blouse instead of the full sari (I don't feel comfortable in saris either). Is there a special piece of jewelry you can wear? If you don't want it to be religious then just have your mom pass the flame over you or whatever, but don't do a full puja.
When I was pregnant my dh wanted to do the hair parting ceremony. It was more of an act of love than any religious obligation. He lovingly parted my hair, and promised to be a good daddy, and that was all there was to it. No big ceremony (and I'm sure we did it all wrong anyway) but lots of meaning.
My oldest is 8 and she identifies herself as an Indian, I think in part because she looks a lot more like my dh than she does like me. She is very comfortable in Hindu/Indian settings, although she's not fully been raised that way. She loves Indian food. I don't look it very well so when we visit with dh's family she just eats it all up until she's stuffed. When we go to temple on festival days she offers to serve food and then eats a big plate herself. It's her favorite part of going to the temple.
She finds the rest a bit boring.
When she was 6 we all traveled to India to see dh's family. None of them live here in the US. It was a very, very important trip for my daughter. Her sister was too young to remember, but my oldest remembers it quite well and wants very badly to go again. She felt that for once she was not a minority, she felt very loved and very much at home. She enjoyed the adventure of traveling, seeing new things, eating new foods. She is proud of that part of her heritage. She was thrilled to see her name used several times as the names of a pharmacy, a hotel, and a goddess at a temple.
Although she's very much an all American girl (into the typical things that an 8 year old is into), has lots of friends, looks forward to American holidays, I am so, so glad that we have exposed her to cultural things. On the other hand she looks forward to visits from the Easter Bunny (non-religious), Santa, the tooth fairy, and loves making Valentines for her friends. It's a good mix that we have going on.
When she was a year old we took her to India and had the traditional head-shaving and ear piercing. She loves to hear the story of how we carried her up the temple path to Tirupati and gave her hair to God like her mother and father before her, and generations before that. It makes her feel very special and important, that we took the time to do that. We had an informal naming ceremony at our home when she was about a month old. Her daddy traced her name in a plate of rice, and then whispered her name into her ear three times. We have photos and she treasures hearing about that.
Whether you are Indian, German, or whatever, rituals are very important. It doesn't have to be about religion necessarily, or about language. It's okay if you don't agree with Hinduism, but the rituals are part of your family's past. If you don't want to be religious, at least share your favorite parts about the holidays, or teach the greater meaning. For Diwali you can celebrate the victory of light over darkness, good over evil. You can keep it that general, but still have fun lighting up your home and cooking a meal to celebrate.
For spring time, maybe incorporate Holi into Easter and celebrate the spring with colors of paint and colored eggs, too. Celebrate Pongal as a harvest festival and invite your friends over for a feast. It doesn't have to be totally authentic.
Your children may or may not want to identify with your culture. At least give them the option. Good luck!