first, welcome to the DIS, disneylover!!
there are quite a few good restaurants in WDW, unfortunately most are pretty expensive.
if you're looking for fun, 50's pime time in MGM can be great! (the waitstaff might lecture your parents about putting their elbows on the table, not cleaning their plate, etc). the waiter/waitress pretends they're part of your family (e.g., aunt betty, cousin joe, uncle tim, etc) & do silly things to tease everyone. the decor is like a 50's style kitchen & really cute. food is more "common", but you could get appetizers or split an entree at lunch & stay within budget.
http://www.wdwinfo.com/wdwinfo/dining/diningdetail.cfm?Restaurant.ID=113#menu
chefs de france (EPCOT-world showcase:france) has very good french food in a nice atmosphere. their lunch menu has a few entrees around $11 (soda normally costs about $3 everywhere)
http://www.wdwinfo.com/wdwinfo/dining/diningdetail.cfm?Restaurant.ID=322
san angel inn (EPCOT-world showcase:mexico) has a few items on their lunch menu between $10-15. atmosphere is interesting, very similar to the "real mexico"

& can have, depending upon the location of your table, a view of boats from mexico's attraction, Rio Del Tiempo, go by

. be forewarned tho: personally we enjoyed the food, but i've heard of a few people who don't like it.
http://www.wdwinfo.com/wdwinfo/dining/diningdetail.cfm?Restaurant.ID=93
tangierine cafe (EPCOT-world showcase:morrocco) is a counter service restaurant, but i'm including it b/c it has "interesting food" and a nice atmosphere (tho it can get crowded). lunch ranges from $8 to $14. we found the portions very generous
http://www.wdwinfo.com/wdwinfo/dining/diningdetail.cfm?Restaurant.ID=223
there are many other choices, but i hope this gives you an idea of what's out there.
my feeling is that you would enjoy chefs de france the most. it has everything you're looking for: nice atmosphere, reasonable price, "non-american" food, & since the waitstaff are french, you can practice some with them!
btw, as with any WDW restaurant, your mom should make an ADR (advance dining reservation).
if you need anymore help, just ask.....a lot of the fun of a trip to WDW is the planning

when are you going?
