"That would be lovely. Would you like me to come with you in case she doesn't settle and we can chat, or would you prefer to just pick her up from school and I pick her up at the end if you have stuff to be getting on with?"
Unless you have a preference in which case
"That would be lovely. Would it be OK if I came the first time as she's not used to play dates" or "That would be lovely, is it OK for you to collect her from school or would you prefer for me to come too?"
Ask the mum incase she's a weird munsnetter with odd rules but at dc school, it would be absolutely unheard of to go with the child. The host collects from school the parent collects at a set time. In half term, I dropped my daughter off and stayed for a cup of tea but that was purely to be sociable
ginteresting I would say that is the norm when they get to year 1, but in Reception many children/parents won't feel comfortable with the child going alone the first time. Plus parents are also often trying to make other parent friends so like the other one to attend. Especially if child is eldest.
I don't have a particular preference and my daughter is very social so I don't think she would be nervous about being there without me. If it was me hosting I'd be more than happy to pick up, but everyones different.
Usually the other parent would collect your child and you would pick up later but on a first school friend playdate, you could go and meet your DD and take her things home so you can check she's still ok about it. It's very early into the reception term for playdates already but also so lovely she's been asked!
It so tedious when the parent stays but I'm speaking as the parent of a Reception child who is very confident about play dates. I fully understand that lots of children aren't ready at this age. Trouble is, my child is constantly inviting other children to our home - usually very loudly when I'm chatting to their parent - and I feel obliged to follow through and then have the child's mother sitting on my sofa for two hours. That's great when it's your first child and it's all novel and fun and life revolves around that one child but when it's not your first and your life is so much busier, play dates are blessed opportunities to have some time to yourself or time to do something else while your child is busy with their friend. This can't happen if the parent tags along.
Anyway, it's entirely up to you. You know if your child is ready. Lots aren't and there's no shame in that.