is it possible to lauch some oozie workflows with only one coordinator?

It depends. If wf1 and wf2 are logically related, have the same frequency and have common dataset dependencies, you can put them by one coordinator (and run them simultaneously or one after another). But if they aren't than it's better to put them in separate coordinators.

You can launch several workflows from one using the sub-workflow feature:

<workflow-app name="root-workflow" xmlns="uri:oozie:workflow:0.4">    <start to="run-wf1"/>    <action name="run-wf1">        <sub-workflow>            <app-path>${appPath}/wf1.xml</app-path>            <propagate-configuration/>        </sub-workflow>        <ok to="run-wf2"/>        <error to="kill"/>    </action>    <action name="run-wf2">        <sub-workflow>            <app-path>${appPath}/wf2.xml</app-path>            <propagate-configuration/>        </sub-workflow>        <ok to="end"/>        <error to="kill"/>    </action>    <kill name="kill">        <message>Action failed, error message[${wf:errorMessage(wf:lastErrorNode())}]</message>    </kill>    <end name="end"/></workflow-app>

If you'd like to run them simultaneously than use forking.