Memorial Day/early that week for Tourist (San Antonio, Austin: hotel, gardens)

[gouldmanj]

Help - I need a bit of advise.
I am flying into San Antonio very late on Sunday night from Boston, alone with my 7yo son for my nephew's graduation in Austin on the 31st. Since we are getting in so late on Sunday, that is a wash.
My in-laws from Austin are willing to drive down and spend the day with us on Monday (Memorial Day) and we are in the middle of the "you decide what you want to do and then we'll all do it" tug of war. Neither of us want to decide.
They will be traveling with their 12yo son and maybe their 17yo too.
What do I have to make sure I don't miss during my trip?

Our hotel is on the Riverwalk so I thought for Tuesday my son and I would do the River Walk, Alamo, maybe Children's Museum (if it gets too hot outside for us Northerners =), Market Square - anything else?
Maybe on Wednesday go to "cowboy country" (Bandera) or go river rafting in Greune.
Then Thursday we are up to Austin for the rest of our stay, except for a sidetrip to the Natural Caves on Sunday after graduation.

So that leaves what to do on Monday.....
I was thinking maybe Brackenridge Park (Witte Museum, Japanese Gardens, Zoo (however, zoo isn't at the top of my list because I could see zoo animals almost anywhere) Will it be too busy, too hot, etc.?
OR
Should we do the Schlitterbahn water park?
OR
SeaWorld? (once again something else I could do in another town)
OR
rafting in Gruene?

Your thoughts would be much appreciated.

Thanks!!!!

Julie

PS - is there a dude ranch/horseback riding in the Gruene area? Maybe on Wednesday I could combine both activities?

[CelesteDF]

I REALLY dislike crowds, although it's a holiday weekend so it will be tough to avoid. However, here are things I definitely would NOT do on Memorial Day:

• The Witte Museum (will likely be mobbed because it's the last day of the Body Worlds exhibit)
• Tubing on the Guadalupe (mobbed by locals who are off for Memorial Day)
• Seaworld, Fiesta Texas or similar tourist attraction

Things I WOULD do on a holiday:

• San Antonio really does have a wonderful zoo & the Japanese Tea Gardens next door are great for wandering, checking out fish and resting
• Tour the Mission trail, and definitely stop at the new visitor center at Mission San Jose
• A Hill Country jaunt, plenty of public/state parks you can go hiking or ranches you can go horseback riding

Tubing, the Witte Museum and theme parks are great on non-holiday days because they're not quite so packed.