Incidentally, children that are graduated to a booster too soon are also at risk of these injuries... children should be a *minimum* of 4 years old *and* 40lbs before going to a booster. A simple backless booster would be fine for a 7 year old as long as the vehicle you are using has head restraints. A backless booster also stores well in a suitcase or as carry-on in the overhead bin (my preferred method so it can't get lost). 
Westjet is excellent with parents using carseats (they actually prefer that you do) and Air Canada is pretty good... we fly out of Calgary.
You need to be careful with the Alpha Omega because the top most position is for *booster mode only*. This will be imprinted on the plastic (difficult to read) on the back of the seat. Most children outgrow this seat by height right around the age of 2.5 - 3 years old because of this rule.
If you want to tell me where his shoulders are in relation to which slot he is using on the Alpha Omega and his height/weight, I can give you some recommendations. Off the top of my head, we (techs) generally recommend the Evenflo Visions/Chase/Traditions or Evenflo Bolero/Generations as good combination seats. The Bolero/Generations will make a better booster than the Visions/Chase/Traditions, but keep in mind that no matter what seat you get, you will eventually need another booster (probably just a $20 backless booster) down the road though.
Both versions of these combination seats harness to 47lbs and then booster to 100lbs. They also have nice tall top slots, so the harness mode should not be outgrown before 5 years old (good booster age). They are also fairly easy to install in most vehicles.
As for the 7 year old... legally, they do not have to be in a booster in California (6 years old OR 60lbs). From a safety aspect, they should be in a booster until they can pass the 5 step test. Children that do not pass the 5 step test are at risk of submarining under the seatbelt causing major stomach injuries that easily lead to death.
The 5 Step Test
If you answer "No" to any of these questions, your child must be in a booster seat:
1. Does the child sit all the way back against the auto seat?
2. Do the child's knees bend comfortably at the edge of the auto seat?
3. Is the lap belt touching the top of the thighs, not the tummy?
4. Is the shoulder belt centered on the shoulder and chest?
5. Can the child stay seated like this for the whole trip?
BELT-POSITIONING BOOSTERS CAN NOT be used with only a lap belt!
(See your car dealer for a lap/shoulder belt retrofit.)
Hope that helps... sorry for the book.
), let me know and I'll walk you through it.Thank you
Hi!
Yeah that to all of the advice that Canadianmom2three gave you.
Just make sure the straps are above your son's shoulders (and it's not in the top most position) and you can use the Alpha Omega no problem. I definitely second the removing the base. Much easier to install/cart around.
At 6 years old, I'd want to keep your daughter in a high back booster for main use. If the vehicle head rest is what's interfering with the install, it can be removed as previously suggested (as long as it's not an Apex combination seat)... if that's not the issue, then maybe a different booster for her would work better. Vehicle year/make/model would help with giving you options to look at for that scenario.
If you need some help on removing the base (and can't find your instructions... a common occurrence
).We had an '03, an '07 (for two weeks) when the '03 was getting repaired, and now own an '08... so I'm pretty familiar with the vehicle.
The head restraints removed may make the seat sit a little more flush with the vehicle seat, but you're right that the '07's head restraints don't generally interfere with booster use.
Booster seats are only meant to raise the child up so that the seatbelt will fit the child correctly. They will all seem more free on the seat. If you have an older booster or a combination seat that has a wider base, I can see how it could seem to move more freely than others.
The Britax Parkway, Evenflo Confidence and Graco Turbobooster all fit on the captain's chairs nicely. The Parkway has been discontinued now (although I love this seat), but the others are easy to find. We also have the new Sunshine Kids Monterey coming out later this summer. It is the only booster that is allowed to be LATCH'ed to the vehicle... which is great because you don't need to remember to buckle up the unoccupied booster. An unbuckled booster could easily become a projectile in a collision, so we always recommend buckling them up at all times. It also has fantastic side impact protection.
The Alpha Omega is definitely allowed to have the base removed for all installations (optional), but *must* be removed for booster use. Their instructions are confusing and not the best unfortunately... it seems to be a recurring theme with most manuals (which would be why I have a job
Depending on which level/date of manufacture of Alpha Omega you have, it will have either a 6 or 8 year expiration date... generally stamped in the plastic on the back of the seat or written in the manual.
With your vehicle and child (2.5 yr old), you could go with any of the options I've suggested in this thread. Sunshine Kids Radian, Evenflo Visions/Chase/Traditions, Evenflo Bolero/Generations. They all install nicely in your van.
