Tre, you can build the frame for the stand for less than 100 bucks if you use 4/4 posts. the weight of the stand will be no problem if you use 6-8 posts cut to 3 ft in length. For the rest of the construction I would use 2/6s. I made a rack with this basic construction for 9 30 gals so that's 270 gals of water. This rack was about 8 ft tall at the top of the tanks that were on it and I feel like it could of held way more weight.
This look like a fun build, good luck and congrats on the lil Tre on the way.