I think its a good idea. Only problem I could see is if anyone in either family is overly attached to their surname. (E.g. I am attached to my family name so had to become a bdouble-barrel when I got married, as there was no way that I was letting go of the name that I grew up with.) If both you and your partner have brothers/sisters/cousins that can "carry-on" your family names, then there shouldn't be any issues with both of you changing yours.