I don't think you can change the automatic variable labels in PROC MEANS to something custom, unfortunately. You can label the variable:
proc means data=sashelp.class;
var age;
label age="Child's Age";
class name;
output out=classmean sum=;
run;
You can use AUTOLABEL to automatically append (default) labels:
proc means data=sashelp.class;
var age;
label age="Child's Age";
class name;
output out=classmean sum= n= /autoname autolabel;
run;
But I don't think you can control it further than that. The easiest solution I can imagine is writing a macro to do it using PROC DATASETS [taking the known variable names and assigning them labels based on those names]. I don't know what you need to make them, but it's not terribly difficult to do. Something like this (the proc sql in particular will vary significantly based on your program).
%macro relabel(var=);
label &var._n = "&var. Count";
*... more of these ...;
%mend relabel;
proc sql;
select cats('%relabel(var=',name,')') into :rellist separated by ' '
from dictionary.columns
where memname='MYDATASET' and libname='WORK' and *criteria to determine in proc means*;
quit;
proc datasets;
&rellist.
quit;