Goldfish will be fine in your water, I'd leave the pH alone.
29 will be a little small when those goldfish grows up. You can prob manage till they get 3-4" each ... but at 6-8" full grown, you will want at least a 75gal. <10 gal per fish is also a bad "rule", it depends on tank shape, depth, etc. Eg. you can stock more in a 40 gal breeder due to its larger surface area. Your 29, being a tall tank, you can stock less.>
For now, just watch the parameters & do your pwc's. If you find the nitrates going up or any accumulation of ammonia or nitrites, you know the tank capacity is being exceeded & time for a new tank.