Under raise a shield there are no additional requirements outside of wielding the shield. It states you get the bonus until the start of your next turn, so I'd say yes, it should work. Bucklers only state you can't raise them if you're holding something in the hand that's heavy, not that you can't then grip something heavy.
While it's not super realistic, I like this change overall because it jives more with how bucklers (targe's...) are used iconically, with two-handed weapons. And because bucklers without this are just so much worse than regular shields...
