Sometimes you cannot win in these situations, it's sad when both parents can't put you 1st for one day.
My dad married his affair partner (who had been my mum's best friend), the ripples continue to bounce around 30 years later.
As with the OP, my sister wanted our dad to come to her wedding on his own, but he refused to come without his new wife. This hung over the whole day, my mum was upset and distressed all day and my dad and his new wife then snuck off early before the meal as they felt they'd been made to feel unwelcome.
My sisters subsequent graduation, was spoilt as this time my dad didn't bring his wife, but was evidently annoyed as he wasn't on good form at all throughout the day (understatement).
Ten years later I graduated, but didn't attend or celebrate at all to avoid a repeat performance.
Another 10 years on I get married, but my mum doesn't come to any part of the day, as she is too traumatised to see my dad and his wife again (literally still traumatised, she's never got over it at all).
My advice - just invite your mum and your dad. Your dad & his wife will get over it, if he doesn't come then it's his loss and he'll go on to regret it.