I grew up in a conservative shul and had massive expectations on me for my Bat Mitzvah - hours and hours of leading, 7 full aliyot, a haftorah, dvar torah... on and on. I grew up at the synagogue so it wasn't difficult, and I actually quite liked the attention!
I am now a member of a liberal congregation and am raising children in a more culturally Jewish way. My daughter is 12 and having her bat mitzvah in November and it's going to be very, very, very different. She's autistic and has anxiety and is finding everything about it to be way too much. I'm teaching her myself for a long list of reasons and we are focussing on learning 3 aliyot and a dvar torah. And if that is still not possible I will do the torah myself and she can write a haftorah and sing along with me. or something else that hasn't occurred to me.
My parents are still quite religious and even they have had to remind me that all Jewish children 'become' a Bar/Bat Mitzvah at 13 (or 12 obviously in some congregations) regardless of any sort of ceremony - they just reach the age. So anything is great, making it a positive experience is great, celebrating your child is great... it can look a lot of different ways.
For my daughter we are keeping the day very simple as she gets overwhelmed quickly. Ceremony with some sort of involvement, an easy (catered) buffet after, a break and then a ceilidh that evening with another easy (catered) finger food buffet with lots of her favourite foods. (We live in Scotland). She's a dancer so is going to create a performance for the evening so she can show off what she is most confident about. She can wear whatever she wants, invite whoever she wants etc.
Even with all this she's still finding it really, really stressful so we'll see what actually happens in the end but I feel strongly that your Rabbi should work with you and your child to ensure this is the start of a good relationship with Judaism as an adult - not something totally stressful that will make them walk away from it later on.