I have gone over a few times in recent seasons with my two young sons. We all joined the MUFC supporters club on line. This may seem expensive, but, it gives young lads or girls a lot of enjoyment. I then applied for tickets on the manutd.com web site for the family section of the ground.
You take a risk by booking flights at the same time. On the last three occasions we have not failed to get tickets, probably due to the fact that we were applying for the family section near the tunnel. If I didn't get the tickets I still intended flying to Manchester on the pre-booked flights and would porobably have bought from local touts... or begged on askaboutmoney.com!
You can also join the Dublin branch of the MUFC supporters club who run trips to all home matches. These are usually over subscribed, but, they do run a fair lottery system and the trips are very well run and great fun. Travel is by boat to Holyhead and bus to Manchester. My lads enjoyed this too, though arriving in at Dublin Port at 06:00 and going straight to school and work nearly killed their Dad! The lads loved it (aged 8 and 13)!
THE big match next year already is Man. U. v. Sunderland!