Here’s a map of the downtown river walk. The ‘X’ is where your hotel and convention center are. The ‘A’ is Acenar. It’s probably half a mile (maybe a smidge more) walk. If the weather is nice and your group is the walking type, then it’s very doable.
The main tourist part is that horseshoe shaped part of the river. Turing right off the horseshoe takes you north on the river towards the Pearl/Arts district. And left goes south toward the historic King William area. The curve of the horseshoe (the ‘x’ area) is the hub of tourism - Alamo, rivercenter mall, convention center, La Villita, and hemisphere park/tower of the Americas.
*hint on Tower: most people purchase a ticket to go to top. However, there is a bar up there with a nice happy hour. If you go around to restaurant hostess stand and tell them you want to get a drink at the bar they’ll take you up there and depending on what you drink, it may be cheaper than the regular ticket to the top (plus you get a cocktail!)