Help please - referring to surnames as a collective. Apostraphe or not?

[TheYearOfTheCat]

Can anyone help? I am writing cards for my DS' christening.

I want to say:

The Smiths would like to invite The Donnellys to . . . . .

Should there be an apostraphe before the s? As in:

The Smith's would like to invite The Donnelly's?

I wouldn't have thought so normally, but I have a nagging doubt that things are different for surnames.

I would be grateful for any advice.

No apostrophe.

No apostrophe, never in a plural, not even for surnames. Definintely.

It's just a straight plural rather than a possessive thingy (or a missing letter)

no

Or use The family to avoid any gaffes?

I mean definitely of course...

Thank you - now I feel silly