I am not a HS coach but was a coach of a HS aged travel team for many years (hung it up this year). We faced the same issues. Most of our HS around here have large field houses so we had no problems finding a gym with lots of room. Lots of hitting and throwing for the pitchers. We had enough space to do some decent long toss as well. Spent lots of time working on fielding situations (ie who covers what in certain situations). We were fortunate enough to layout a diamond with 90' base paths. Also, lot of grounders to the infielders. As well as some base running situations.