Was it sudden or did your mum know it was coming and expressed views on what she wanted? I sympathise, it will be 7 years tomorrow since my mum died and she was adamant at wanting cremation not burial, if your mum had very strong views on what she wanted and it wasn't a sudden passing, i'm sure she would have told you.
Also, please try not to stress too much about it, as it will never be "perfect". The man who did my mums service actually read out completely the wrong birth date, and my aunt got up to give a speech and it was all about her not my mum, going on about events my mum was present for, but focused on my aunt, like banging on about some bag my mum had bought for her, but describing the bag and how much she loved it, my mums mention simply bring she paid for it. My aunt is also religious but my mum and dad weren't so it was strictly a no religion service but my aunt was mentioning god, heaven etc in her speech. I tried to veto her speech as she sent a copy a day or two prior to the funeral but my dad (who had the final say on everything) didn't want to rock the boat and so let her do it, but was so angry after that he didn't tell her no, and all my dads side of the family were commenting after how selfish and self centred her speech was.
BUT, in the end, it didn't matter what anyone around me was saying, because all that really mattered was that there was a crematorium, packed full with loads more people stood outside who there wasnt room for, all there, just to remember and say goodbye to my mum. I spent most of the time in my own head with my own thoughts, unintentionally, and couldn't really focus all that much on what everyone else was saying and doing.