Front row_ can sometimes sit a bit low depending on stage height. Front half of stalls is usually good, nearer the centre as possible.
Front of grand circle gives good veiws of the whole stage, good if child is a bit unsure of the charactors, (far enough away from them).
Upper circle, starts to get a bit high and don't feel as involved. Somestimes called rear circle if it is the back section of the circle.
Gallery, can be very high and scares some adults, stairs can be very steep and lacking in hand rails, not good if carrying babies or toddlers or if pregnant. Not good if they like to get out of seat and jump about. Great if you like abseiling or base jumping.
Ends of rows are good for getting out to toilet and dancing in the ailse which is Ok if they will stay nearby, not so good if they keep making a run for it and you spend the whole time jumping up to chase after them.
TOP TIPS
Take your own drinks and snacks. (Some venues don't like you taking in sealed bottles but most don't mind for kids shows), cartons are good if your kids don't squeeze them, best to take their usual cups.
Don't give too much to drink too early, or you will be in the loo the whole time.
Don't take crisps or I will crack up, so noisy . Chocolate can get a bit messy in a warm theatre too.
If you don't have a lightweight booster fold up your jacket into a pad, put inside childs jacket and zip up. Gives a good solid cushion that won't fall to bits and gives enough height for children to see better.
Take a fireman (or what ever the charactor is for the show) surprise toy, unless you don't mind buying a expensive thing from the merchandise stall. Perhaps get 2 small toys and wrap them up, give one once you sit down to keep them amused until the lights go down and save the other one for emergencies or for when they are all tired and teary when it ends.