We started putting our mare/foal out with the other horses when our foal was about two weeks old. We still keep them housed separate, but put them out with the others when ever we can (we have no pasture, and mare/foal require so much more food!). Our horses all got along pretty well before she foaled, so putting her in with the geldings was tense while she told them off, but they all quickly settled in. Our one gelding took over as a babysitter and the other is really intimidated by the foal (who loves harassing him :) ).
The only advise I could give about getting a halter on would be to get as much hands on time with the foal as you can until he is relaxed with you being around him and touching him...it might make haltering easier. Working with mom too, might make baby curious about you enough to let you work with him.