We go quite regularly and went recently at the start of August. We usually love it but it wasn't the best trip because we ended up going on a day when it was 30c.
Understandably the indoor enclosures had queues to limit numbers but the queues were outside with no shade so we didn't do many because it was just too hot to queue with a baby in a pram. So that's something to keep in mind because you might end up standing around in the sun/rain for a good half an hour for some of the more popular enclosures like the apes and jaguars.
This was our first time going with a baby, it's very pram friendly, couple of steep hills but it's fine. Only enclosure I found you can't take a pram in was the lemurs, there is a buggy park outside but my little boy was asleep in his pram so we didn't end up going in.
Also not all indoor enclosures are open the aquarium and bat's were both still closed. The boat ride around the islands is also closed.
I've just realised I sound quite negative but I just wanted to make you aware of a few bits. I'm sure you'll have an amazing day as even with a few bits closed it's still an amazing day out, especially if you've not been before.