I believe, if you can at all manage it, that attending a reception is essential to officiating at a wedding. It's where the party is at, it's where Jesus was at (caveat: we need not always ask WWJD, but in the case of John 2 and the wedding at Cana, it's not bad to consider whether he was role modeling). It's where people who attended the wedding take time to process it with you if you're available to do that. It's an opportunity for pastoral care and counseling with the friends and relatives of the bride and groom, and often it's your last chance to coach them on how to be a community around the bride and groom, bride and bride, or groom and groom, in their life together. Receptions aren't just or even primarily for the couple. They're an opportunity to build up the whole group in their communitas.
I can't stress enough how important that is, and how important receptions are both as an evangelistic opportunity as well as a pastoral ministry. By all means, go, if invited!
I have, on average, had two or three families who were at weddings end up joining our church following their participation in the wedding. Sometimes this is joining, sometimes this is re-engaging congregational life. It's in the top five strategies I can think of to add members to your church. And remember, often married couples start having babies, or are young and energetic with spiritual gifts to share... Even if it's a second or late in life marriage, there are many transitional things happening in their family life that can use a word from God and presence by a leader in Christ's church.
I also publicize my availability as a pastor to do weddings in our congregation and community, advertise it on appropriate web sites (such as, for example, this blog), chat up area reception hall coordinators, etc. about routing people my way, everything I can do to connect.
If you are an introvert (I am half and half extro and intro), then just schedule recoup time into the next week. If you have a wedding, just take a whole extra day off the week following. Then, be open to being at everything they invite you to. But don't just be present. Prepare and pray so you have faith-filled conversations.
My family comes along on some receptions, in which case it's also a chance for tasty treats and dancing! Since I don't drink, I find you can leave early, because once alcohol is flowing, then the opportunities for pastoral care and counseling diminish somewhat. At that point I let others who are more comfortable in drinking situations take over the Christian presence.
Oh, and I simply love weddings! I feel blessed each time I have the chance to officiate and coach a couple in preparation for their marriage.