Looking for kanji for my babies' names (Seiji & Kenji)

Hi,
I hope somebody can help me. I named my baby twins "Seiji" and "Kenji", and I am looking for the corresponding kanjis. I already found some of the kanjis that could be used, but obviously not all of them would make sense or are not appropriate for a name.
Could you please help me telling me which kanjis would be vaild to use for those names? Or what would be the most common way to write them in Japanese? I'm just looking for the right way to write them, and that has an interesting meaning (not just "second child" for example).
Thank you very much! I look forward for your comments.
This is what I found for "SEI":
1 世
2 井
3 制
4 勢
5 声
6 姓
7 婿
8 征
9 性
10 情
11 成
12 政
13 整
14 斉
15 星
16 晴
17 正
18 清
19 牲
20 生
21 盛
22 省
23 精
24 聖
25 背
26 脊
27 製
28 西
29 誓
30 誠
31 請
32 逝
33 青
34 静
35 鯖
This is what I found for "KEN":
1 件
2 倹
3 健
4 兼
5 券
6 剣
7 圏
8 堅
9 嫌
10 建
11 憲
12 懸
13 検
14 権
15 犬
16 献
17 県
18 研
19 絹
20 繭
21 肩
22 見
23 謙
24 賢
25 軒
26 遣
27 鍵
28 間
29 険
30 顕
31 験
And this is what I found for "JI":
1 事
2 似
3 侍
4 児
5 地
6 字
7 寺
8 慈
9 持
10 時
11 次
12 治
13 滋
14 璽
15 磁
16 示
17 耳
18 自
19 辞
20 除

Here are your choices for Seiji
名前の響き（読み）から命名「せいじ」（1）

And here is Kenji
名前の響き（読み）から命名「けんじ」（1）

there are 3 pages worth for Kenji, just click on the numbers.

BTW.. why do you what to know this? are they of Japanese descent?
Please tell me it is not because you wanna get a tattoo... or try to make their names written legally with Kanji...

Thank you!

I'll check for the meaning now.

About the reason, yes, my grandparents were Japanese, so they would be the third generation born outside Japan in the family.