Just because you are going back to work doesn’t mean you have to wean. You could still nurse at bedtime. For naps maybe find a new routine that does not involve nursing and something his caregiver could easily do with him, that way it won’t be a big change. If you are only nursing him those two times a day, you could continue to nurse him to bed and pump at work when he would usually nap so that your supply stays the same or chose to only nurse at bedtime. Your body may regulate to just that one nursing session. Another thing to consider is if you are not used to pumping, introducing it now may not be effective.
Is he going to daycare? If so he will be fine! They sleep better at daycare especially when they see everyone else doing it. You don't have to wean!