What are the visa options for a family in Thailand on a 30-day exemption while applying for ED visas?

Me, my wife and four little kids are staying in Thailand (Pattaya) on 30-days exempt, which will expire in two weeks on 31/08. Me and my wife would like to apply for ED-visa (Eng language course), but we need to wait 3 weeks my language school will do the paperwork…

So here are the questions:

1) in order to get papers from school here in Thailand, should we do a border-run and get another 30-days exempt, or we can go to Immigration and extend for 7 days? or 30 day? Not sure how much days allowed, but probably 7 days will not be enough.

We all are Russian passport holders.

2) which Consulate in neighbor country is better to go and in lower risk of ED-visa been denied nowdays?

At this moment, we don’t have right for mistake since me and my wife will do our ED-Visa trips one-by-one while second of us is watching kids here in Pattaya. We don’t want to take all our kids aboard for visa run because of triple the cost.

3) Is it good idea to keep kids in Thailand instead of making dependent (“O” I guess) visas? They are exempt from overstay fee, but they might be blacklisted if they will stay 6-8 month overstay? Which means, if we will go aboard for a trip, there is a chance that they will be denied in entrance back to Thailand, right?

Please help!

Our travel history to Thailand: We have a single visa exempt stamp in our new passports. It is the first entry in the last 6-8 years. Before that (8 years ago) we both had ED-visas (Eng language course) for 2 years and before that had 2-3 times 30-days exempt entries, not back-to-back, but year or so apart. These all in our old passports.