I wouldn't recommend letting them out together for playtime. That could very well end up in a fight and setting the bonding process back(or ruining it completely). Changing spaces, putting them in an area one rabbit has claimed as his territory from previously being in that space(before properly neutralizing and making changes), or expanding the bonding space too much too quickly, could all result in increased territorial behavior and a fight breaking out.
Usually it's best to keep things in a smaller neutral space for bonding, then gradually expanding that space as the rabbits spend more time together and are doing well together. If you have to change the bonding area, they'll usually need an adjustment period and there may be a slight backtrack in their progress. Usually starting the space smaller is best, then only expanding that space when there has been consistent positive progress between them.
This is just generally what works best for most bonds. But there are instances where other methods work better for some pairs. So if you feel things aren't progressing well, or if they're worsening, it may be time to reevaluate and make changes. But for now it sounds like what you're doing is working out, so best to keep going with that, gradually increasing their time together and gradually expanding their space, and not making any sudden changes if possible.
https://rabbitsindoors.weebly.com/bonding-bunnies.html
https://cottontails-rescue.org.uk/information/bonding-bunnies/
https://wabbitwiki.com/wiki/Bonding_rabbits_together