Hrm, damn, I don't know if I have any on-hand, but somewhere. I would say beige coat over pink shirt and blue pants will look a little washed-out, since you're covering up large blocks of color with a large swath of neutral. I think it's better if the situation is inverted. I think Madras patch is much cooler and more fun, and in that case the beige jacket would work well to tone the whole look down. I think that would look good.
I would say to keep it light and loose, but it really depends on the vibe the hosts are going for -- beach formal can mean anything from linen/cotton suit and tie to shorts and polo -- so I think it best to mix up more casual elements with more formal. I would say to skip the knit tie with the above looks, since it would be dressing it up a bit. If you had an outfit (such as the cotton suit) that would be dressed down by the knit tie, then I'd say go for it. I think if you do go for a knit tie, maybe a darker color paired with a similarly colored boldly striped shirt would be not garish but still fun and lively (e.g. navy tie with navy/white bengal-striped shirt).
What I've done for this sort of thing is to wear all linen -- beige or grey-blue pants or shorts with a white or slate-grey shirt and a striped beige jacket, patterned square. Linen manages to both dress it up and down simultaneously, whereas cotton can be ambiguous as to what you're going for. White pants also go a long way to making such looks work -- pair with a fun-colored solid shirt and a neutral jacket and you're good to go.
Do you have a "thrift fit" or any "beach formal" pic?
Pre-pics thrift fit tomorrow, but thinking: Beige Cotton Sport Coat, over a Pink shirt with Light Blue Incotex Pants (or Madras Patch?) and White Bucks. Knit Tie but not sure yet. Also just picked up a J Crew Ludlow Cotton suit......so many options. Anyone got some beach formal thirft fit pics?