Well I think you answered a bit of your own question in thinking about the big milestones he is going through. This always makes it challenging for bed time. Because he is doing so many big boy things that take him away from you during the day and at night, you might try giving him more mommy time in the day - like holding him more, carrying him in a sling for errands, etc (Dr. Sears).

The only other suggestion I can think of is buying him a stand alone potty to use in his room right before bedtime. This way it is in his room and is less of an inconvenience for you and eventually, you can tell him he can use it himself. In addition, this may also eliminate his request all together if your suspicion is right and he is just asking to go to get some more mommy time.

I hope this phase is over soon!
Nisha