The play equipment centrally placed with seating all round.
Easy access for parents to rescue upset/scared kiddies or staff available to do this for you.
Screens to view your children whilst on the equipment
Separate toddler/ under 5's/ children's areas.
Hands-on play equipment in a separate area for babies e.g, building blocks etc.
Comfy seating, free papers and magazines
Healthy food and a place that doesn't stink of chip fat (like the one in Fleet I went to yesterday)!
Drinks at reasonable prices and shelves to put them on, at a height that kids can't knock them over or kick them over when some twit leaves a boiling hot cup of coffee on the floor.
Toilets with more than 2 cubicles and sinks low enough for children to reach.
Separate hand-washing area placed near the cafe.
Baby change facilities and nappies for sale in case of being caught short.
Notice board for advertising stuff for sale.
Plenty of parking on site or close by.
For parties, a good sized party room with prices that reflect the quality of what you'll get to eat and the party bags containing something other than cheap plastic rings or copious bags of Haribos...how about fruit bars and raisins? Also discounts on drinks for those booking a party (dd's party cost me £29.50 on top for drinks for the parents).
Access to drinking fountains.
we have 3 round here of which I tend to only visit one which is the best of an OK bunch. The other two stink of wee and chip fat and the floor of the toddler area in one was covered in trodden in chips and tomato sauce.
Another idea, is to have a facility for private parties which you could do at specific times e.g. early evenings for older children (aged 7+).
Can you tell that I've been thinking about this idea as well?