Lincoln certainly delayed McDowell's march on Richmond to divert troops into the Shenandoah, but as far as the troops meant to go to McClellan that didn't because of the concern for the capital, here's the AotP counting the Washington defenses and the troops in the Shenandoah as of the beginning of April:
http://ebooks.library.cornell.edu/cgi/t/text/pageviewer-idx?c=moawar;cc=moawar;q1=for duty;rgn=full text;idno=waro0014;didno=waro0014;view=image;seq=0055
McCall and Franklin from 1st Corps are addressed below:
http://ebooks.library.cornell.edu/cgi/t/text/pageviewer-idx?c=moawar;cc=moawar;q1=Franklin;rgn=full text;idno=waro0014;didno=waro0014;view=image;seq=0092 and Blenker's division (which McClellan refers to as 10,000 men strong).
http://ebooks.library.cornell.edu/cgi/t/text/pageviewer-idx?c=moawar;cc=moawar;q1=April 5;rgn=full text;idno=waro0012;didno=waro0012;view=image;seq=0297
Per McClellan here, the organization above consisted of 85,000 men (per his message here:
http://ebooks.library.cornell.edu/cgi/t/text/pageviewer-idx?c=moawar;cc=moawar;q1=85,000;rgn=full text;idno=waro0012;didno=waro0012;view=image;seq=0029 ). But given that he felt that Johnston had 100,000 men and that Johnston had the advantages of fortifications - do you see him moving faster against a foe believed to be 100,000 men strong if he had (85,000+10,000+33,510) 128,510 men?
Also, see this:
http://ebooks.library.cornell.edu/cgi/t/text/pageviewer-idx?c=moawar;cc=moawar;q1=Magruder;rgn=full text;idno=waro0012;didno=waro0012;view=image;seq=0025
I'm not saying Lincoln did everything right - and trying to trap Jackson in the Valley the way he did was not as great an idea as it sounded in his head. But McClellan's own decisions seem to indicate that even if he had all the men he asked for he would not have advanced aggressively if his understanding of the enemy's strength went from Magruder having 15-20,000 men not counting Huger vs. his 58,000 ready to march on April 3 to "probably" 100,000 on the 7th.
McClellan might not have been an utter fool, but he was not the general to smash enemy armies like a hammer.
I hope that the number of messages here doesn't feel overwhelming.