Keeping them separated until after your male has recovered from his neuter is the right idea, however I will caution having them right next to each other. Rabbits can fight through bars, and especially putting him in your female’s territory of the dog crate, there’s a good chance she might try to take a large bite of his nose. I have seen bunnies that have been bitten through bars before, sometimes it requires surgery. If is better if you can have a distance of about 4 inches between the playpen and dog crate wire so that they can’t reach their noses through to nip each other. They may not act in this way but it’s better for their safety just in case. Otherwise having one in the dog crate and the other in the pen is a good option. You could also swap them between them every few days so that your male will get to stretch his legs in the pen and it also provides the benefit of pre-bonding and swapping scents and making them share cages.
When you do start to bond them, make sure that you introduce them on neutral terroritory 