Angels do get 6" but they are very thin fish and do not create that much waste. A pair can even live in a 20 gallon although I suggest at least 29 gallons. The chinese algae eater, and parrot fish will cause some problems. The paradise fish can get agressive, watchout for that. The chinese algae eater will get big and aggresive. Pet stores lie about these animals. Parrot cichlids get huge! Instead of the chinese algae eaters, get otos (really cute your kids would love them), or dwarf plecos (not the common variety!) but clown, rubber nose, or bristle nose plecos.
When you switch over tanks, try to save most of the old water and fish in big plastic containers. Then you can use the old gravel, plus some new gravel in the 29 gallon. fill with the old water (probably 15-20 gallons), then fill up the rest with declorinated water. Use the old filter. You don't even need to cycle the tank.