My kids will go to school in Phuket, so they will have ED and we would get the O visa after them.
We would like to go home 2 times a year at least (for Xmas and all summer).
Im thinking about to buy Thai Elite visa because I hate running in and out of immigration offices, but I dont know that in this case with an ED+O, plus the frequent traveling how difficult it would be. Thank you for your help.

You can get a re-entry permit on ED and O, which means you come back on the same stamp, you don’t need to get a new visa. You’d then do annual extensions of both. The only tricky bit is that you have to be IN Thailand to do it, at some point during that month. If you are outside Thailand when your stamp and re-entry permit runs out, you would then need to get a new visa.