Husband and I have a legal marriage, but didn't have the whole big deal day. Now getting marriage blessed my the church and getting things done right. Do I need to wear cream/ivory? or can I wear white? Also how would I go about wording the invites? It will only be immediate family and a couple close friends.
Re: Convalidation Service
Fatty Blog
As long as you're keeping it small, and your reception is along the fancy meal lines (no bouquet toss, garters, big introductions etc) it's appropriate to celebrate the occasion. Don't register, no showers, etc. It's an important church occasion, so think of it like celebrating a first communion or confirmation and you won't go far wrong.
Previously Alaynajuliana
You could do simple, hand-written invites that just give time/date/place for the ceremony. Don't have attendants. Wear a nice, non-poufy dress. Don't do any of the trappings of a wedding (bouquet toss, garter toss, etc.). If you have it around a meal time, invite everyone out for a meal or over to your house for a meal, no potluck.
I agree the Catholic board would be a great spot to get some additional info (presuming you're Catholic b/c I'm unaware of any other religions doing convalidations). Also you should definitely check with your priest if there are any requirements - I know in my home church convalidations are not supposed to be a big thing, so they would frown on a wedding dress, but different parishes have different rules.
Regardless, I don't think a formal invitation would be out of place, but should be consistent with the reception afterward just like any other event. What StarMoon said sounds good.
Ditto going to the Catholic board and also just keep it understated. Most Catholic churches do not want a couple to confuse a Convalidation with a ceremony of two people who aren't legally wed already.