In San Antonio you could try the Westin Riverwalk (downtown on river, new), The Plaza-Marriott (very nice, near river, great for your size group), Westin La Cantera (not on river, but a new resort property and very nice) or Hyatt Hill Country Resort (not anywhere near the river or anything else but Sea World, but a wonderful place to stay/meet). Marriott has a couple of hotels on the river (Rivercenter-huge and River Walk-just fairly large), but both are fairly large and your group will likely be surrounded by larger groups. Hope this helps. (If you've got any more questions, let me know -- I do meeting planning for my nonprofit association.)