I think I may be too lax about this stuff. DD sometimes has things like fishfingers, potato shapes, beans, tinned spagetti, etc. at nursery. But not every day. It may be just one meal in the week - others include chicken dinners, homemade cotage pie of casseroles, etc. Puddings range from fruit, yoghurt, 'proper' puddings and custard, rice puddings, etc.
Teas are high tea things like fruit, raw veggies, sandwiches, pancakes, cheese and crackers/rice cakes, crumpets, etc...
I just think that this is fine as it isn't every day. DD (just 2) has had similar menu at nursery - goes 2 days a week - since she started on proper solids. She eats very well, is in no way over weight or too thin, she loves her food and will try almost anything. I just think that so long as things are done in moderation and are balanced throughout the week then it's fine.
If you are concerned of salt content int hings like beans, why not ask the nursery about their policy on salt/fat/nutrional balance?