How would you present this to your child if you were in my shoes? He's 10 years old, and pretty much all of 4th, 5th, and 6th grade math he has been unhappy about how easy and "boring" it is.
I would first try to get the details on how the summer sessions will work, just so you can give those to him as facts. If you can't get that info beforehand, that's ok, just tell him you don't know yet, but for my kids, it helps to have that type of info up front - even if it really doesn't factor into their decision. They just like to see it as a plan, rather than "if you choose ____, you'll have to do ___, but I can't tell you exactly how or when or where you'll do _____".
Then I'd just give him the choices, without added excitement or any kind of warnings about extra work. If he says he's not sure or doesn't know what he wants to do, make a pros/cons list with him (and this is where you can insert anything you want to remind him of such as being bored in his current class etc). Then help him go through the decision making process looking over his list.
The last thing I'll throw in there - in our family, we make sure we get input from our children in decisions like this and when we can we like to let them make the decision, but we also, depending on the decision, make it clear that parents' decisions are sometimes the last call. That sounds dictatorial doesn't it - but it's not meant to be. It's just that some decisions really do belong with the parent - either because we understand the situation or know more about what's the right thing to do simply based on our life experience - or it might be a decision that's too big or too stressful for our child to make. If you think either of these apply here, just make the decision for him and explain your reasons.
I'll also add - don't know if it will help you feel more confident with your decision or not but fwiw - although this may be the first time it's been tried at your ds' school, moving higher ability math students into Algebra in 7th grade isn't uncommon in our district, and in some ways there's been a bit of a "push" for it. It's really worked out a-ok, and I think in the situation your ds is in where the school district is offering tutoring to fill in the gaps it's a win-win all around. The only thing I'd want clarified before saying "yes" was to make sure that scheduling works out, and also would want to know that he'll be able to move on to Geometry in 8th without any superficial bumps in the road such as "we don't offer Geometry at his middle school" etc.
Best wishes,
polarbear
