As far as I know, this is the most widely used translation. I would then work around the 'college'. An alternative is 'Mayor and executive board' in which case you could refer to the board'. The iamsterdam.nl site uses 'Mayor and college of alderman' so you could then refer to the 'college' but I don't think it sounds right in English. Depends a lot of course on the target audience.

I am translating a (EU-policy) text about Rptterdam (EN>NL), and this is the term they are using for "Burgermeester en wethouders"

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Note added at 1 hr (2010-06-04 10:43:36 GMT)
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Ik bedoel natuurlijk Mayor and Vice Mayors (Mayor zonder "S")

The mayor chairs both the city council and the council of mayor and aldermen. The council of mayor and aldermen exercise the executive power of the ...
http://en.wikipedia.org/wiki/Municipal_politics_in_the_Nethe...

The mayor chairs both the council of mayor and aldermen and the city council. He is a member of the council of mayor and aldermen (college van burgemeester en wethouders)
http://en.wikipedia.org/wiki/Burgemeester

Its main role is laying down the guidelines for the policy of the council of mayor and aldermen and exercising control over its execution
http://wapedia.mobi/en/City_Council_(Netherlands)

The projects d'amenagement communal are formulated by the Council of Mayor and Aldermen. They are submitted to the Planning Commission, attached to the ...
http://books.google.co.uk/books?id=SnLloLYVJl0C&pg=PA195&lpg...

The same requirements exist as at the national level: the Council of Mayor and Aldermen act on issues where, at the national level, the Administration acts
http://www.iniref.org/netherlands.html

15 Dec 2009 ... The Council of Mayor and Aldermen has decided to financially support the organisation of the sixth European Universities Rowing Championship
http://www.eucr2010.nl/node/34

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Note added at 2 hrs (2010-06-04 11:22:55 GMT)
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These various citations all address the question of how the term is translated into English when it applies to the Netherlands, as I assume Barbara's Source Text does.

this is how I often translate this, and it is one of the terms given in Van den Ende juridische lexicon, and on various websites with specific reference to the Dutch legislative body.
Here's one explanation: The mayor and the aldermen make up the Municipal Executive (college van burgemeester en wethouders).

After the municipal elections, which are held every four years, the Municipal Council (Gemeenteraad) appoints the aldermen (wethouders) based on the number of representatives elected from each party. Together with the mayor (burgemeester), the aldermen make up the Municipal Executive (College van B&W). The Municipal Executive is responsible for the day-to-day administration of the city, on the basis of a joint four-year policy programme.

Then there's the wikipedia definition:
The college van burgemeester en wethouders (abbreviated as college van B&W or simply B&W) is the executive board of a municipality in the Netherlands. This local government body plays a central role in municipal politics in the Netherlands. It consists of the mayor (burgemeester) and the members of the municipal executive (wethouders). Belgium has a similar system, which is referred to as the college van burgemeester en schepenen in the Dutch language.

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Note added at 22 hrs (2010-06-05 07:34:59 GMT)
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Oops, sorry about that example sentence mishap. my copying and pasting skills are only up to snuff after a few cups of coffee.