AIBU to want my kids to learn their language of their home country?

[BowieFan]

Bit of background.

DS1 and DS2 are twins and are not from this country originally. We adopted them at birth from Bulgaria and they have been citizens here for all of their lives. In the past 18 months I've been trying to get them to at least go and have some Bulgarian language lessons so they can speak to their biological grandparents (whom we are in contact with) with more ease. They've been going but the teacher is now leaving and we're looking for somewhere else to have the lessons.

DS1 isn't that bothered to having more, DS2 just goes along with what he says. DP thinks it's up to them if they want to keep learning or not.

I'm firmly of the opinion that they should keep going. We're their parents but I don't want them to forget their heritage or be ashamed of it. I feel like in the future they might want to look into their bioligical family more and they might regret not learning the language in years to come.

AIBU or not?

Slight update:

Spoke to DS1 and DS2 this morning. Both sad to hear that they won't be able to keep going after Christmas as apparently they've both been really enjoying it. They both want to continue but DS1 said he would prefer it if they could fit it in around his football schedule instead of him having to miss his Wednesday training. I think the best idea will be to find a tutor who can do it via skype for some grammar lessons, as I think they're fulfilling the "every day usage" thing by going there for holidays and speaking to their GPs every week.