I think it's quite an expensive weekend trip but it is possible to make things cheaper
I would recommend staying in an off-site hotel to save money, as I have heard they do very good deals - maybe not quite as themed as the Disney hotels but definitely worth it if you're on a budget.
If you've got a breakfast included with that, it might be worth seeing if you can take some breakfast items out with you. At the Disney hotels they do a buffet-style breakfast and sometimes we take a few bread rolls or croissants out with us. It's quite nice to have a snack at about 11am and not worry about having to buy anything! Same with taking an empty plastic bottle with you and using the water fountains to save buying new drinks every time you get thirsty.
It also might be worth having one big meal and one smaller meal per day - if you eat loads at a buffet restaurant at lunchtime, then you can have a sandwich or something in the evening which will be a lot cheaper
Also - if you're not too fussy about when you go, some people sell their tickets on eBay, if they weren't able to take the trip or had spare tickets, etc. I haven't done this myself but it might be useful to have a little look, and see if there are any slightly cheaper tickets going?