Help me furnish this room as a combined kids playroom and home office

First of all, do you think it’s a good idea to combine these two rooms into one in this space? This room has an en suite full bathroom, so it could be a bedroom, but I feel that because of its attic-y space it’s more suited for a playroom. We also need an office space and don’t have a separate room to dedicate to it. So we either combine playroom and an office or guest room and an office. Which would you choose?

If you’d combine playroom and office, would you do built in custom cabinets for the office?

Thank you!!