Translation:We would be delighted to come to the party.
Basen ni = We would be
wrth ein boddau = In our element/Really happy/Delighted
i ddod= to come
i'r parti = to the party
I get that but I have no idea what that means in English. It’s my native language and this sentence still makes no sense.
*wrth ein boddau * which is translated as 'in our element' is an idiom in UK English, here's a definition :- http://dictionary.cambridge.org/dictionary/english/be-in-your-element
This sentence could also be transposed as 'We would be delighted to come to the party'
Hope that helps