The options as I see them:
1. If your mom is OK with a limo or a taxi, keep the current ADR (You could totally surprise her and be in the limo waiting for her, which might be pretty cool).
2. If your mom is more comfortable sticking with ME, change to the 4:10 so the kids get the GG experience but keep trying for a later time, too. It sounds like the 5:20 isn't going to work unless Mom is OK with option #1, so changing to the 4:10 doesn't hurt you and you can still try for later.
Talk to your mom and see how much taking ME matters to her and go from there.
1. If your mom is OK with a limo or a taxi, keep the current ADR (You could totally surprise her and be in the limo waiting for her, which might be pretty cool).
2. If your mom is more comfortable sticking with ME, change to the 4:10 so the kids get the GG experience but keep trying for a later time, too. It sounds like the 5:20 isn't going to work unless Mom is OK with option #1, so changing to the 4:10 doesn't hurt you and you can still try for later.
Talk to your mom and see how much taking ME matters to her and go from there.