Hi Robin,
I was on on Tobago for a 2 week family holiday in late July 2006. North American migrants were as expected very thin on the ground at that time with no passerines, only a single Osprey & a few waders seen. Of the waders we had spotted Sandpiper & Semi-palm. Plover on our hotel beach. The sewage works near the airport had a few Lesser Yellowlegs, a Greater Yellowlegs, Stilt Sandpiper, Dowitcher spp & vagrant Wilson's Phalarope (another birder saw it but it was gone by the time I got there).
I'VE been to Trinidad in May but not August. The shuttle between the two islands is cheap, frequent & ehhh quaint! If planning a trip to Trinidad try to book 3 nights at the Asa Wright Centre -theirs is a full-board package so its not that cheap BUT they will provide the Trinidad airport transfers & the birding at AWC is amazing. There is enough there to keep non-birders satisfied for a few days (my non-birding wife stayed there with me for a week & thoroughly enjoyed it). If you are contemplating the AWC make sure you stay for a minimum of three nights as this qualifies you for a free guided trip to see the Oilbirds. You can also do a half-day trip to Caroni swamp from the AWC & in august the Scarlet Ibis numbers should be buoyant providing a stunning birding spectacle.
If you haven't yet booked Tobago accommodation then choose carefully. We stayed at Arnos Vale which was reasonably okay quality-wise but the local birding was excellent. Other places offer better accommodation but poorer local birding. If possible hire a car for part of your stay so that you can visit Grafton Estate & the local sewage works (car hire wasn't expensive & they drive on the left).
Check out this site for further info:
http://www.trinoutdoors.com/pages/birding_hotspots.htm
If you need/want further info please feel free to contact me by private message.
To give you an idea of what I saw on Tobago check here:
http://www.pbase.com/rainbirder/tobago
For Trinidad check here:
http://www.pbase.com/rainbirder/trinidad
Whilst going to AWC on Trinidad will undoubtedly increase the cost of your holiday, doing this will turn your family holiday into a birding holiday to remember > Bearded Bellbird, Channel-billed Toucan, lekking Manakins, 3 species of Trogon, Oilbirds, Antbirds (Great Ant-shrike & Black-faced Ant-thrush @ AWC), Scarlet Ibis, possible Ornate Hawk Eagle, White Hawk, Black Hawk.........
