Living in Colchester I would also recommend it. There are plenty of good primary schools but these all tend to be oversubscribed. As your younger 2 are both infant age the maximum class size of 30 will apply so finding a place will be the biggest problem - especially for both in the same school which I expect you would want!
The other thing to bear in mind if you are thinking of public transport to school for your DD is that unlike CRGS, Col CHS is not really walkable from the town centre. The best bus route within colchester is the first bus no. 65 (highwoods to stanway) so maybe looking at areas along that route if you can't move within walking distance (house prices quite high in that area!)
(I also have a DD starting there in sept)
thank you very much for the reply! And the heads up on the bus service, i will surely keep all this information. As for my two younger ones, i suspected getting them into the same school might be a challenge, but like they say: Keep calm and carry on! is the best option for now.
Many thanks once again for the advice, hey! won't it be great that our girls might meet up! Congratulations on your DD's achievement and every ones out there.