Just thought I'd throw my two cents in:
We're getting married in three months, and our AHR is about a month after that. I also come from a big European family (I'm Greek and my FI is Ukrainian) and we've come upon many of the issues you have with regards to "etiquette." I've had to remind my mom over and over that the same wedding "etiquette" does NOT apply to DWs!!!
We've already had the big, Greek engagement party in Toronto (about 100 people), to celebrate with my family and friends there. We did serve a plated dinner, hire a dj, have our priest bless our rings in a special ceremony, give bombinierre (favours), have a seating chart, etc. It was, in essence, a mini-wedding, very formal, I wore a beautiful floor-length cocktail dress and my FI was in a three-piece suit.
Our AHR is taking place in Edmonton, where my FI and his family are from, and will have about 300 people, predominately his side, and our friends from Calgary. I will NOT be wearing my dress. thinking it was "tacky" never really crossed my mind, but rather that my wedding dress is special, only something I want to wear on my wedding day; so for me, it was more a feeling of it being "inappropriate." Our reception is not a "wedding," just like our engagement party wasn't. There will be a dinner at the AHR (buffet-style) and a band. I am doing favours for the AHR, but not as costly/fancy as those for our e-party (we gave crystal mosiac glass candleholders). Partly due to the fact that the e-party was way more per per guest, and partly because it was more formal. My AHR will be WAY more casual, and I'm making homemade jam that I'll be canning in pretty little mason jars - it just fits the theme better.
Ultimately, you have to do what you are comfortable with!!!! Anything goes