Let your feelings guide you. If you wanna stand up, stand up, if you wanna kneel, kneel. Be warned though, my mum is a midwife and he reckons there are some lazy ones who will want you to just stay on the bed.
With my last child, I didnt want to kneel at all and my midwife was instant that I should. I of course ignored her and lay on my side as this felt most comfortable and she very sarcily tld me I would get nowhere like that, 3 cms to fully dilated in 5 hours..... I Was like hahahaha!!
You wil be smitten when you see your baby.
Good luck x