I think it's natural to be ambivalent. It is like a bomb going off in your lives and your marriage in the first year. You need to be a team to make it a success and while it sounds like the two of you are in a great place to start a family it's worth doing your due diligence.
Out of interest, have the two of you actually sat down and done the maths on having children and tested your respective assumptions?
What are your respective maternity and paternity paid leave periods?
How long do each one of you want to take off? Does your husband assume you will do it all?
Back to work? Do you want to return? Does your husband assume you will/won't? If you change your mind what then?
Will his earnings allow for a pension fund for you? Will yours if he wants to be a SAHD ? Does he presume you will be at home and not him? Would he entertain working compressed hours over a 4 day week so you both have one day at home with the kids? Useful to test thinking especially if you don't have friends with small kids and aren't already considering how the will impact your lives other than "it would be nice to have a mini-me and take a son to the rugby"
Have you got sufficient savings to fund that period? Redundancy is a real risk during pregnancy and maternity leave.
Childcare? Visited any nurseries and established a) places availability and b) cost?
Grandparents - have they made vague supportive statements about "helping out". If they have what does that actually look like in practice? [there are a million threads on here about GP's backing off or simply being a nightmare ignoring parents requests] I would be frank - you've suggested many times you would look after a grandchild. How many days a week? From 8am to 6pm? Do you take the child to them or do they come to you? How does that work with a commute for you both - who will do drop offs and pick ups? For how long? You still need wrap around care when school starts - if anything it's harder.
School - do you have any strong views on state versus private? If the latter, do you have sufficient income bandwidth to start saving serious cash amounts to be able to fund it in 5 years [on top of childcare costs]?
As someone in their early 50's with children in their teens there are a lot of pro's to having children in late 20's/early 30's. I can remember my parents turning 40 in my teens. My kids were toddlers. I will be retiring when they finish university. It is unlikely I will ever take them hiking in South America, my knees are knackered.😂
It is very easy to put it all off and enjoy these years but you may regret it later.
Equally, it's also very easy to end up with several small children, a spouse who doesn't pull their weight and divorced by 40 with years out of the workforce.
Children are very hard work but usually very rewarding. Consciously choose to have them, both of you.
A wise woman once said, "Men want children like children want a dog". Not all men I hasten to add, but many are not prepared to put the work in.