Usually with Vistaprint you can change existing text on invites. You can change the "Together With Their Families" to Mr & Mrs Knottie #s. Traditionally an invitation only lists the hosts of the event, not a whose who of the B&G's families.
Are your parents hosting the wedding? Then they should be properly listed as such.
Did you even attempt to customize it? I didn't fiddle with the spacing but yes, you can add hosts. The spacing might be an issue because you can't move that stupid brown dot in the middle.
That was a weird DD. I'm usually good at quoting, but I didn't think it was anything worthy of a DD. OP did mention that her FI's parents are deceased, so maybe that's why she DD.
Re: How to address "hosts" on invitations