Heavy Appetizer Reception

I think a 7 or later start time is fine, especially if guests know in advance and there truly are a ton of appetizers.

Not necessarily true. You can have an heavy apps reception anytime as long as there are enough apps per person to equal a full meal if they are heavy apps

Heavy appetizers (or hearty appetizers) would mean hot or cold appetizers that would be enough for a meal: skewers of shrimp or meat; wings; small grilled lamb chops; rollups or wraps; meatballs; smoked salmon

or 6-8 bites per person per hour or 24-32 bites per person for a four hour reception. you would be surprised how fast you get full