Family advice needed

So, long long story short, I haven't had a relationship with my father in about 2.5 years. If anyone is interested in specifically why not, I'm happy to answer questions, but the basic reason is that the negativity of the relationship was seeping into basically every aspect of my life. We tried family therapy, and in therapy he told me that I could like it or leave it. I chose to leave it. We've texted and emailed every couple of months over the last 2.5 years, mostly one-liners like "Happy Birthday," but there's been no other contact.

My fiance proposed in May. I called my father that day and left a voicemail telling him we got engaged. He called back (I legitimately missed the call) and left a voicemail saying congrats.

When we booked a venue, I sent an email to the family, including my dad, linking to the venue's website. I got excited responses from my sister, brother, & former step-mother (who's essentially my mother - another long story). It's been about 3 or 4 weeks, and I've had no response from my father. My brother thinks I didn't get a response because my dad didn't like my finacee (they met like, 3 or 4 times before we stopped talking).

Maybe I am getting ahead of myself, since my wedding isn't going to be until October 2013. But I am really conflicted about how to handle my dad's role, or lack thereof, in my upcoming wedding. I don't have any particular intention of mending fences before the wedding, unless he initiates the mending (which I do not expect).

Would it be in bad taste to ask my brother to walk me down the isle? I plan to invite my father to the wedding (it's up to him if he wants to come or not - I think it's the right thing to do regardless of his decision). I think it would embarass him in front of the rest of my family and my fiance's family if he wasn't a part of the ceremony, but I genuinely feel like it would be a sham to invite him to participate at this point.